31339921 has 2 divisors, whose sum is σ = 31339922. Its totient is φ = 31339920.

The previous prime is 31339883. The next prime is 31339933. The reversal of 31339921 is 12993313.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 22429696 + 8910225 = 4736^2 + 2985^2 .

It is an emirp because it is prime and its reverse (12993313) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31339921 - 2⁷ = 31339793 is a prime.

It is not a weakly prime, because it can be changed into another prime (31331921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15669960 + 15669961.

It is an arithmetic number, because the mean of its divisors is an integer number (15669961).

Almost surely, 2^31339921 is an apocalyptic number.

It is an amenable number.

31339921 is a deficient number, since it is larger than the sum of its proper divisors (1).

31339921 is an equidigital number, since it uses as much as digits as its factorization.

31339921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4374, while the sum is 31.

The square root of 31339921 is about 5598.2069450852. The cubic root of 31339921 is about 315.2820887883.

The spelling of 31339921 in words is "thirty-one million, three hundred thirty-nine thousand, nine hundred twenty-one".