31312021309 has 2 divisors, whose sum is σ = 31312021310. Its totient is φ = 31312021308.

The previous prime is 31312021283. The next prime is 31312021373. The reversal of 31312021309 is 90312021313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 29415680100 + 1896341209 = 171510^2 + 43547^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31312021309 is a prime.

It is a super-3 number, since 3×31312021309³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31312021409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15656010654 + 15656010655.

It is an arithmetic number, because the mean of its divisors is an integer number (15656010655).

Almost surely, 2^31312021309 is an apocalyptic number.

It is an amenable number.

31312021309 is a deficient number, since it is larger than the sum of its proper divisors (1).

31312021309 is an equidigital number, since it uses as much as digits as its factorization.

31312021309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 972, while the sum is 25.

The spelling of 31312021309 in words is "thirty-one billion, three hundred twelve million, twenty-one thousand, three hundred nine".