31157681 has 2 divisors, whose sum is σ = 31157682. Its totient is φ = 31157680.

The previous prime is 31157677. The next prime is 31157689. The reversal of 31157681 is 18675113.

31157681 is nontrivially palindromic in base 8.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19536400 + 11621281 = 4420^2 + 3409^2 .

It is a cyclic number.

It is not a de Polignac number, because 31157681 - 2² = 31157677 is a prime.

It is a super-2 number, since 2×31157681² = 1941602170595522, which contains 22 as substring.

It is a Chen prime.

It is equal to p_1925087 and since 31157681 and 1925087 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (31157689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15578840 + 15578841.

It is an arithmetic number, because the mean of its divisors is an integer number (15578841).

Almost surely, 2^31157681 is an apocalyptic number.

It is an amenable number.

31157681 is a deficient number, since it is larger than the sum of its proper divisors (1).

31157681 is an equidigital number, since it uses as much as digits as its factorization.

31157681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5040, while the sum is 32.

The square root of 31157681 is about 5581.9065739226. The cubic root of 31157681 is about 314.6697841298.

The spelling of 31157681 in words is "thirty-one million, one hundred fifty-seven thousand, six hundred eighty-one".