31709921 has 2 divisors, whose sum is σ = 31709922. Its totient is φ = 31709920.

The previous prime is 31709911. The next prime is 31709927. The reversal of 31709921 is 12990713.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27040000 + 4669921 = 5200^2 + 2161^2 .

It is a cyclic number.

It is not a de Polignac number, because 31709921 - 2²² = 27515617 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (31709927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15854960 + 15854961.

It is an arithmetic number, because the mean of its divisors is an integer number (15854961).

Almost surely, 2^31709921 is an apocalyptic number.

It is an amenable number.

31709921 is a deficient number, since it is larger than the sum of its proper divisors (1).

31709921 is an equidigital number, since it uses as much as digits as its factorization.

31709921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 31709921 is about 5631.1562755796. The cubic root of 31709921 is about 316.5179809212.

The spelling of 31709921 in words is "thirty-one million, seven hundred nine thousand, nine hundred twenty-one".