31397257 has 4 divisors (see below), whose sum is σ = 31409536. Its totient is φ = 31384980.

The previous prime is 31397243. The next prime is 31397273. The reversal of 31397257 is 75279313.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 75279313 = 409 ⋅184057.

It is a cyclic number.

It is not a de Polignac number, because 31397257 - 2⁷ = 31397129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31397287) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 693 + ... + 7954.

It is an arithmetic number, because the mean of its divisors is an integer number (7852384).

Almost surely, 2^31397257 is an apocalyptic number.

It is an amenable number.

31397257 is a deficient number, since it is larger than the sum of its proper divisors (12279).

31397257 is an equidigital number, since it uses as much as digits as its factorization.

31397257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12278.

The product of its digits is 39690, while the sum is 37.

The square root of 31397257 is about 5603.3255304328. The cubic root of 31397257 is about 315.4742398910.

The spelling of 31397257 in words is "thirty-one million, three hundred ninety-seven thousand, two hundred fifty-seven".