31249991 has 2 divisors, whose sum is σ = 31249992. Its totient is φ = 31249990.

The previous prime is 31249979. The next prime is 31249993. The reversal of 31249991 is 19994213.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31249991 is a prime.

Together with 31249993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31249993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15624995 + 15624996.

It is an arithmetic number, because the mean of its divisors is an integer number (15624996).

Almost surely, 2^31249991 is an apocalyptic number.

31249991 is a deficient number, since it is larger than the sum of its proper divisors (1).

31249991 is an equidigital number, since it uses as much as digits as its factorization.

31249991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17496, while the sum is 38.

The square root of 31249991 is about 5590.1691387649. The cubic root of 31249991 is about 314.9802322356.

The spelling of 31249991 in words is "thirty-one million, two hundred forty-nine thousand, nine hundred ninety-one".