31172209 has 2 divisors, whose sum is σ = 31172210. Its totient is φ = 31172208.

The previous prime is 31172201. The next prime is 31172243. The reversal of 31172209 is 90227113.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 30835809 + 336400 = 5553^2 + 580^2 .

It is a cyclic number.

It is not a de Polignac number, because 31172209 - 2³ = 31172201 is a prime.

It is a super-2 number, since 2×31172209² = 1943413227879362, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (31172201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15586104 + 15586105.

It is an arithmetic number, because the mean of its divisors is an integer number (15586105).

Almost surely, 2^31172209 is an apocalyptic number.

It is an amenable number.

31172209 is a deficient number, since it is larger than the sum of its proper divisors (1).

31172209 is an equidigital number, since it uses as much as digits as its factorization.

31172209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 31172209 is about 5583.2077697324. The cubic root of 31172209 is about 314.7186839209.

The spelling of 31172209 in words is "thirty-one million, one hundred seventy-two thousand, two hundred nine".