31978913 has 2 divisors, whose sum is σ = 31978914. Its totient is φ = 31978912.

The previous prime is 31978889. The next prime is 31978927. The reversal of 31978913 is 31987913.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21687649 + 10291264 = 4657^2 + 3208^2 .

It is a cyclic number.

It is not a de Polignac number, because 31978913 - 2⁸ = 31978657 is a prime.

It is equal to p_1972598 and since 31978913 and 1972598 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (31978013) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15989456 + 15989457.

It is an arithmetic number, because the mean of its divisors is an integer number (15989457).

Almost surely, 2^31978913 is an apocalyptic number.

It is an amenable number.

31978913 is a deficient number, since it is larger than the sum of its proper divisors (1).

31978913 is an equidigital number, since it uses as much as digits as its factorization.

31978913 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40824, while the sum is 41.

The square root of 31978913 is about 5654.9900972504. The cubic root of 31978913 is about 317.4104585575.

The spelling of 31978913 in words is "thirty-one million, nine hundred seventy-eight thousand, nine hundred thirteen".