66904409 has 12 divisors (see below), whose sum is σ = 79198308. Its totient is φ = 56142240.

The previous prime is 66904393. The next prime is 66904457. The reversal of 66904409 is 90440966.

It can be written as a sum of positive squares in 2 ways, for example, as 14992384 + 51912025 = 3872^2 + 7205^2 .

It is not a de Polignac number, because 66904409 - 2⁴ = 66904393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66904459) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19694 + ... + 22839.

It is an arithmetic number, because the mean of its divisors is an integer number (6599859).

Almost surely, 2^66904409 is an apocalyptic number.

It is an amenable number.

66904409 is a deficient number, since it is larger than the sum of its proper divisors (12293899).

66904409 is a wasteful number, since it uses less digits than its factorization.

66904409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42568 (or 42557 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 38.

The square root of 66904409 is about 8179.5115379832. The cubic root of 66904409 is about 405.9615601776.

The spelling of 66904409 in words is "sixty-six million, nine hundred four thousand, four hundred nine".