31216891 has 2 divisors, whose sum is σ = 31216892. Its totient is φ = 31216890.

The previous prime is 31216877. The next prime is 31216897. The reversal of 31216891 is 19861213.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 31216891 - 2⁵ = 31216859 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (31216897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15608445 + 15608446.

It is an arithmetic number, because the mean of its divisors is an integer number (15608446).

Almost surely, 2^31216891 is an apocalyptic number.

31216891 is a deficient number, since it is larger than the sum of its proper divisors (1).

31216891 is an equidigital number, since it uses as much as digits as its factorization.

31216891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 31.

The square root of 31216891 is about 5587.2077999659. The cubic root of 31216891 is about 314.8689838956.

The spelling of 31216891 in words is "thirty-one million, two hundred sixteen thousand, eight hundred ninety-one".