72978809 has 2 divisors, whose sum is σ = 72978810. Its totient is φ = 72978808.

The previous prime is 72978799. The next prime is 72978817. The reversal of 72978809 is 90887927.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70644025 + 2334784 = 8405^2 + 1528^2 .

It is a cyclic number.

It is not a de Polignac number, because 72978809 - 2⁸ = 72978553 is a prime.

It is not a weakly prime, because it can be changed into another prime (72977809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36489404 + 36489405.

It is an arithmetic number, because the mean of its divisors is an integer number (36489405).

Almost surely, 2^72978809 is an apocalyptic number.

It is an amenable number.

72978809 is a deficient number, since it is larger than the sum of its proper divisors (1).

72978809 is an equidigital number, since it uses as much as digits as its factorization.

72978809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 508032, while the sum is 50.

The square root of 72978809 is about 8542.7635458322. The cubic root of 72978809 is about 417.8934753696.

The spelling of 72978809 in words is "seventy-two million, nine hundred seventy-eight thousand, eight hundred nine".