31321309 has 2 divisors, whose sum is σ = 31321310. Its totient is φ = 31321308.

The previous prime is 31321289. The next prime is 31321313. The reversal of 31321309 is 90312313.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19829209 + 11492100 = 4453^2 + 3390^2 .

It is a cyclic number.

It is not a de Polignac number, because 31321309 - 2¹⁵ = 31288541 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31321309.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31321319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15660654 + 15660655.

It is an arithmetic number, because the mean of its divisors is an integer number (15660655).

Almost surely, 2^31321309 is an apocalyptic number.

It is an amenable number.

31321309 is a deficient number, since it is larger than the sum of its proper divisors (1).

31321309 is an equidigital number, since it uses as much as digits as its factorization.

31321309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 22.

The square root of 31321309 is about 5596.5443802404. The cubic root of 31321309 is about 315.2196636974.

The spelling of 31321309 in words is "thirty-one million, three hundred twenty-one thousand, three hundred nine".