665644401 has 24 divisors (see below), whose sum is σ = 1027952640. Its totient is φ = 413594496.

The previous prime is 665644381. The next prime is 665644457. The reversal of 665644401 is 104446566.

665644401 is a `hidden beast` number, since 6 + 6 + 5 + 644 + 4 + 0 + 1 = 666.

It is not a de Polignac number, because 665644401 - 2⁹ = 665643889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (665644481) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5361 + ... + 36878.

It is an arithmetic number, because the mean of its divisors is an integer number (42831360).

Almost surely, 2^665644401 is an apocalyptic number.

It is an amenable number.

665644401 is a deficient number, since it is larger than the sum of its proper divisors (362308239).

665644401 is a wasteful number, since it uses less digits than its factorization.

665644401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42365 (or 42362 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The square root of 665644401 is about 25800.0852905567. The cubic root of 665644401 is about 873.1337206548.

The spelling of 665644401 in words is "six hundred sixty-five million, six hundred forty-four thousand, four hundred one".