31978861 has 2 divisors, whose sum is σ = 31978862. Its totient is φ = 31978860.

The previous prime is 31978831. The next prime is 31978867. The reversal of 31978861 is 16887913.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 31696900 + 281961 = 5630^2 + 531^2 .

It is a cyclic number.

It is not a de Polignac number, because 31978861 - 2⁷ = 31978733 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31978867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15989430 + 15989431.

It is an arithmetic number, because the mean of its divisors is an integer number (15989431).

Almost surely, 2^31978861 is an apocalyptic number.

It is an amenable number.

31978861 is a deficient number, since it is larger than the sum of its proper divisors (1).

31978861 is an equidigital number, since it uses as much as digits as its factorization.

31978861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 43.

The square root of 31978861 is about 5654.9854995393. The cubic root of 31978861 is about 317.4102865134.

The spelling of 31978861 in words is "thirty-one million, nine hundred seventy-eight thousand, eight hundred sixty-one".