31391957 has 2 divisors, whose sum is σ = 31391958. Its totient is φ = 31391956.

The previous prime is 31391951. The next prime is 31391989. The reversal of 31391957 is 75919313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20376196 + 11015761 = 4514^2 + 3319^2 .

It is an emirp because it is prime and its reverse (75919313) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31391957 is a prime.

It is a Chen prime.

It is equal to p_1938647 and since 31391957 and 1938647 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31391957.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31391951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15695978 + 15695979.

It is an arithmetic number, because the mean of its divisors is an integer number (15695979).

Almost surely, 2^31391957 is an apocalyptic number.

It is an amenable number.

31391957 is a deficient number, since it is larger than the sum of its proper divisors (1).

31391957 is an equidigital number, since it uses as much as digits as its factorization.

31391957 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25515, while the sum is 38.

The square root of 31391957 is about 5602.8525770361. The cubic root of 31391957 is about 315.4564877292.

The spelling of 31391957 in words is "thirty-one million, three hundred ninety-one thousand, nine hundred fifty-seven".