661780100 has 36 divisors (see below), whose sum is σ = 1437241344. Its totient is φ = 264494880.

The previous prime is 661780099. The next prime is 661780117. The reversal of 661780100 is 1087166.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 182909 + ... + 186491.

Almost surely, 2^661780100 is an apocalyptic number.

It is an amenable number.

661780100 is an abundant number, since it is smaller than the sum of its proper divisors (775461244).

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

661780100 is a wasteful number, since it uses less digits than its factorization.

661780100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5444 (or 5437 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 661780100 is about 25725.0869775012. The cubic root of 661780100 is about 871.4408238510.

The spelling of 661780100 in words is "six hundred sixty-one million, seven hundred eighty thousand, one hundred".