31397999 has 2 divisors, whose sum is σ = 31398000. Its totient is φ = 31397998.

The previous prime is 31397939. The next prime is 31398007. The reversal of 31397999 is 99979313.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 31397999 - 2²⁴ = 14620783 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31397939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15698999 + 15699000.

It is an arithmetic number, because the mean of its divisors is an integer number (15699000).

Almost surely, 2^31397999 is an apocalyptic number.

31397999 is a deficient number, since it is larger than the sum of its proper divisors (1).

31397999 is an equidigital number, since it uses as much as digits as its factorization.

31397999 is an evil number, because the sum of its binary digits is even.

The product of its digits is 413343, while the sum is 50.

The square root of 31397999 is about 5603.3917407228. The cubic root of 31397999 is about 315.4767250342.

The spelling of 31397999 in words is "thirty-one million, three hundred ninety-seven thousand, nine hundred ninety-nine".