31266721 has 2 divisors, whose sum is σ = 31266722. Its totient is φ = 31266720.

The previous prime is 31266713. The next prime is 31266731. The reversal of 31266721 is 12766213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31136400 + 130321 = 5580^2 + 361^2 .

It is an emirp because it is prime and its reverse (12766213) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31266721 - 2³ = 31266713 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31266721.

It is not a weakly prime, because it can be changed into another prime (31266701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15633360 + 15633361.

It is an arithmetic number, because the mean of its divisors is an integer number (15633361).

Almost surely, 2^31266721 is an apocalyptic number.

It is an amenable number.

31266721 is a deficient number, since it is larger than the sum of its proper divisors (1).

31266721 is an equidigital number, since it uses as much as digits as its factorization.

31266721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 28.

The square root of 31266721 is about 5591.6653154494. The cubic root of 31266721 is about 315.0364314964.

The spelling of 31266721 in words is "thirty-one million, two hundred sixty-six thousand, seven hundred twenty-one".