72731209 has 2 divisors, whose sum is σ = 72731210. Its totient is φ = 72731208.

The previous prime is 72731203. The next prime is 72731273. The reversal of 72731209 is 90213727.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 40921609 + 31809600 = 6397^2 + 5640^2 .

It is a cyclic number.

It is not a de Polignac number, because 72731209 - 2³ = 72731201 is a prime.

It is not a weakly prime, because it can be changed into another prime (72731201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36365604 + 36365605.

It is an arithmetic number, because the mean of its divisors is an integer number (36365605).

Almost surely, 2^72731209 is an apocalyptic number.

It is an amenable number.

72731209 is a deficient number, since it is larger than the sum of its proper divisors (1).

72731209 is an equidigital number, since it uses as much as digits as its factorization.

72731209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 72731209 is about 8528.2594355472. The cubic root of 72731209 is about 417.4203349975.

The spelling of 72731209 in words is "seventy-two million, seven hundred thirty-one thousand, two hundred nine".