31157991 has 24 divisors (see below), whose sum is σ = 48825504. Its totient is φ = 19069440.

The previous prime is 31157983. The next prime is 31158013. The reversal of 31157991 is 19975113.

It is not a de Polignac number, because 31157991 - 2³ = 31157983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31157911) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3790 + ... + 8756.

It is an arithmetic number, because the mean of its divisors is an integer number (2034396).

Almost surely, 2^31157991 is an apocalyptic number.

31157991 is a deficient number, since it is larger than the sum of its proper divisors (17667513).

31157991 is a wasteful number, since it uses less digits than its factorization.

31157991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5031 (or 5028 counting only the distinct ones).

The product of its digits is 8505, while the sum is 36.

The square root of 31157991 is about 5581.9343421434. The cubic root of 31157991 is about 314.6708277174.

The spelling of 31157991 in words is "thirty-one million, one hundred fifty-seven thousand, nine hundred ninety-one".