31315993 has 2 divisors, whose sum is σ = 31315994. Its totient is φ = 31315992.

The previous prime is 31315981. The next prime is 31316003. The reversal of 31315993 is 39951313.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21279769 + 10036224 = 4613^2 + 3168^2 .

It is an emirp because it is prime and its reverse (39951313) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31315993 is a prime.

It is not a weakly prime, because it can be changed into another prime (31315913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15657996 + 15657997.

It is an arithmetic number, because the mean of its divisors is an integer number (15657997).

Almost surely, 2^31315993 is an apocalyptic number.

It is an amenable number.

31315993 is a deficient number, since it is larger than the sum of its proper divisors (1).

31315993 is an equidigital number, since it uses as much as digits as its factorization.

31315993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10935, while the sum is 34.

The square root of 31315993 is about 5596.0694241584. The cubic root of 31315993 is about 315.2018291667.

The spelling of 31315993 in words is "thirty-one million, three hundred fifteen thousand, nine hundred ninety-three".