661404 has 12 divisors (see below), whose sum is σ = 1543304. Its totient is φ = 220464.

The previous prime is 661393. The next prime is 661417. The reversal of 661404 is 404166.

661404 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661404.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27547 + ... + 27570.

2⁶⁶¹⁴⁰⁴ is an apocalyptic number.

It is an amenable number.

661404 is an abundant number, since it is smaller than the sum of its proper divisors (881900).

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

661404 is a wasteful number, since it uses less digits than its factorization.

661404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55124 (or 55122 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 661404 is about 813.2674836731. The cubic root of 661404 is about 87.1275708076.

The spelling of 661404 in words is "six hundred sixty-one thousand, four hundred four".