661804 has 36 divisors (see below), whose sum is σ = 1383480. Its totient is φ = 274560.

The previous prime is 661777. The next prime is 661823. The reversal of 661804 is 408166.

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

661804 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7392 + ... + 7480.

It is an arithmetic number, because the mean of its divisors is an integer number (38430).

2⁶⁶¹⁸⁰⁴ is an apocalyptic number.

It is an amenable number.

661804 is an abundant number, since it is smaller than the sum of its proper divisors (721676).

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

661804 is a wasteful number, since it uses less digits than its factorization.

661804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130 (or 115 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 661804 is about 813.5133680524. The cubic root of 661804 is about 87.1451314337.

The spelling of 661804 in words is "six hundred sixty-one thousand, eight hundred four".