31139809 has 2 divisors, whose sum is σ = 31139810. Its totient is φ = 31139808.

The previous prime is 31139807. The next prime is 31139821. The reversal of 31139809 is 90893113.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 30195025 + 944784 = 5495^2 + 972^2 .

It is a cyclic number.

It is not a de Polignac number, because 31139809 - 2¹ = 31139807 is a prime.

Together with 31139807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (31139807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15569904 + 15569905.

It is an arithmetic number, because the mean of its divisors is an integer number (15569905).

Almost surely, 2^31139809 is an apocalyptic number.

It is an amenable number.

31139809 is a deficient number, since it is larger than the sum of its proper divisors (1).

31139809 is an equidigital number, since it uses as much as digits as its factorization.

31139809 is an odious number, because the sum of its binary digits is odd.

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

The square root of 31139809 is about 5580.3054575892. The cubic root of 31139809 is about 314.6096079142.

The spelling of 31139809 in words is "thirty-one million, one hundred thirty-nine thousand, eight hundred nine".