31997431 has 2 divisors, whose sum is σ = 31997432. Its totient is φ = 31997430.

The previous prime is 31997429. The next prime is 31997473. The reversal of 31997431 is 13479913.

It is a weak prime.

It is an emirp because it is prime and its reverse (13479913) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31997431 - 2¹ = 31997429 is a prime.

It is a super-2 number, since 2×31997431² = 2047671181199522, which contains 22 as substring.

Together with 31997429, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31997131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15998715 + 15998716.

It is an arithmetic number, because the mean of its divisors is an integer number (15998716).

Almost surely, 2^31997431 is an apocalyptic number.

31997431 is a deficient number, since it is larger than the sum of its proper divisors (1).

31997431 is an equidigital number, since it uses as much as digits as its factorization.

31997431 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20412, while the sum is 37.

The square root of 31997431 is about 5656.6271752697. The cubic root of 31997431 is about 317.4717142636.

The spelling of 31997431 in words is "thirty-one million, nine hundred ninety-seven thousand, four hundred thirty-one".