31121309 has 2 divisors, whose sum is σ = 31121310. Its totient is φ = 31121308.

The previous prime is 31121291. The next prime is 31121341. The reversal of 31121309 is 90312113.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31114084 + 7225 = 5578^2 + 85^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31121309 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31121399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15560654 + 15560655.

It is an arithmetic number, because the mean of its divisors is an integer number (15560655).

Almost surely, 2^31121309 is an apocalyptic number.

It is an amenable number.

31121309 is a deficient number, since it is larger than the sum of its proper divisors (1).

31121309 is an equidigital number, since it uses as much as digits as its factorization.

31121309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 162, while the sum is 20.

The square root of 31121309 is about 5578.6475959680. The cubic root of 31121309 is about 314.5472929234.

The spelling of 31121309 in words is "thirty-one million, one hundred twenty-one thousand, three hundred nine".