31193991 has 20 divisors (see below), whose sum is σ = 49053400. Its totient is φ = 19700496.

The previous prime is 31193971. The next prime is 31193999. The reversal of 31193991 is 19939113.

It is not a de Polignac number, because 31193991 - 2⁵ = 31193959 is a prime.

It is a nude number because it is divisible by every one of its digits.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31193999) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 8596 + ... + 11673.

It is an arithmetic number, because the mean of its divisors is an integer number (2452670).

Almost surely, 2^31193991 is an apocalyptic number.

31193991 is a deficient number, since it is larger than the sum of its proper divisors (17859409).

31193991 is a wasteful number, since it uses less digits than its factorization.

31193991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20300 (or 20291 counting only the distinct ones).

The product of its digits is 6561, while the sum is 36.

The square root of 31193991 is about 5585.1580998213. The cubic root of 31193991 is about 314.7919714901.

The spelling of 31193991 in words is "thirty-one million, one hundred ninety-three thousand, nine hundred ninety-one".