661556080 has 20 divisors (see below), whose sum is σ = 1538118072. Its totient is φ = 264622400.

The previous prime is 661556059. The next prime is 661556083. The reversal of 661556080 is 80655166.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661556083) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4134646 + ... + 4134805.

Almost surely, 2^661556080 is an apocalyptic number.

It is an amenable number.

661556080 is an abundant number, since it is smaller than the sum of its proper divisors (876561992).

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

661556080 is a wasteful number, since it uses less digits than its factorization.

661556080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8269464 (or 8269458 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 37.

The square root of 661556080 is about 25720.7324934575. The cubic root of 661556080 is about 871.3424819166.

The spelling of 661556080 in words is "six hundred sixty-one million, five hundred fifty-six thousand, eighty".