31809139 has 2 divisors, whose sum is σ = 31809140. Its totient is φ = 31809138.

The previous prime is 31809137. The next prime is 31809163. The reversal of 31809139 is 93190813.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31809139 - 2¹ = 31809137 is a prime.

Together with 31809137, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (31809133) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15904569 + 15904570.

It is an arithmetic number, because the mean of its divisors is an integer number (15904570).

Almost surely, 2^31809139 is an apocalyptic number.

31809139 is a deficient number, since it is larger than the sum of its proper divisors (1).

31809139 is an equidigital number, since it uses as much as digits as its factorization.

31809139 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 34.

The square root of 31809139 is about 5639.9591310576. The cubic root of 31809139 is about 316.8477576700.

The spelling of 31809139 in words is "thirty-one million, eight hundred nine thousand, one hundred thirty-nine".