Thirty One (31)
1. It is a prime number.
2. It is the sum of five powers of 2.
2^0 + 2^1 + 2^2 + 2^3 + 2^4 = 31
3. It is the third Mersenne prime.
2^5 – 1 = 31
4. January, March, May, July, August, October, December have 31 days.
5. Sum of first 31 odd primes is a perfect square.
3 + 5 + 7 + 11 + …. + 83 + 87 + 89 = 31^2
6. It is a Centered Pentagonal number.
7. It is a repdigit in base 5 and base 2.
(111)5 = (11111)2 = 31
8. The numbers 31, 331, 3331, 33331, 333331, 3333331, and 33333331 are all prime but 333333331 is not a prime.
9. It can be partioned into 6842 ways.
10. It is amongst the two known number that can be written in 2 ways as the sum of successive powers starting with 1.
31 = 1 + 5 + 5^2 31= 1 + 2 + 2^2 + 2^3 +2^4
11. It is the sum of first two primes raised to themselves.
31 = 2^2 +3 ^3
12. The digit sum of 31st Fibonacci number (1346269) is 31
1 + 3 + 4 + 6 + 2 + 6 + 9 = 31
13. The number obtained by raising the first four prime to themselves comes out to be a prime.
14 . It is a Happy Prime. A happy prime is a number that is both happy and prime.
The first happy primes are 7, 13, 19, 23, 31, 79 etc.
A happy number is defined in the following way:-- Start with any number, replace the number
by the sum of the squares of its digits. Repeat the process until you get 1.
15. It is the minimal move required to solve the Tower of Hanoi puzzle with 5 disks.
Send Your Comments to
Dr Rajesh Thakur
rkthakur1974@gmail.com
1. It is a prime number.
2. It is the sum of five powers of 2.
2^0 + 2^1 + 2^2 + 2^3 + 2^4 = 31
3. It is the third Mersenne prime.
2^5 – 1 = 31
4. January, March, May, July, August, October, December have 31 days.
5. Sum of first 31 odd primes is a perfect square.
3 + 5 + 7 + 11 + …. + 83 + 87 + 89 = 31^2
6. It is a Centered Pentagonal number.
7. It is a repdigit in base 5 and base 2.
(111)5 = (11111)2 = 31
8. The numbers 31, 331, 3331, 33331, 333331, 3333331, and 33333331 are all prime but 333333331 is not a prime.
9. It can be partioned into 6842 ways.
10. It is amongst the two known number that can be written in 2 ways as the sum of successive powers starting with 1.
31 = 1 + 5 + 5^2 31= 1 + 2 + 2^2 + 2^3 +2^4
11. It is the sum of first two primes raised to themselves.
31 = 2^2 +3 ^3
12. The digit sum of 31st Fibonacci number (1346269) is 31
1 + 3 + 4 + 6 + 2 + 6 + 9 = 31
13. The number obtained by raising the first four prime to themselves comes out to be a prime.
14 . It is a Happy Prime. A happy prime is a number that is both happy and prime.
The first happy primes are 7, 13, 19, 23, 31, 79 etc.
A happy number is defined in the following way:-- Start with any number, replace the number
by the sum of the squares of its digits. Repeat the process until you get 1.
15. It is the minimal move required to solve the Tower of Hanoi puzzle with 5 disks.
Send Your Comments to
Dr Rajesh Thakur
rkthakur1974@gmail.com
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