661645404 has 36 divisors (see below), whose sum is σ = 1911420784. Its totient is φ = 189041472.

The previous prime is 661645399. The next prime is 661645409. The reversal of 661645404 is 404546166.

661645404 is a `hidden beast` number, since 6 + 6 + 1 + 645 + 4 + 0 + 4 = 666.

It is an interprime number because it is at equal distance from previous prime (661645399) and next prime (661645409).

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661645409) 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, 1312537 + ... + 1313040.

Almost surely, 2^661645404 is an apocalyptic number.

It is an amenable number.

661645404 is an abundant number, since it is smaller than the sum of its proper divisors (1249775380).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661645404 is a wasteful number, since it uses less digits than its factorization.

661645404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2625594 (or 2625589 counting only the distinct ones).

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

The square root of 661645404 is about 25722.4688550691. The cubic root of 661645404 is about 871.3816966788.

The spelling of 661645404 in words is "six hundred sixty-one million, six hundred forty-five thousand, four hundred four".