661155555500 has 72 divisors (see below), whose sum is σ = 1587166893312. Its totient is φ = 240420180000.

The previous prime is 661155555469. The next prime is 661155555517. The reversal of 661155555500 is 5555551166.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a zygodrome in base 10.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5403596 + ... + 5524595.

Almost surely, 2^661155555500 is an apocalyptic number.

It is an amenable number.

661155555500 is an abundant number, since it is smaller than the sum of its proper divisors (926011337812).

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

661155555500 is a wasteful number, since it uses less digits than its factorization.

661155555500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10928232 (or 10928209 counting only the distinct ones).

The product of its (nonzero) digits is 562500, while the sum is 44.

The spelling of 661155555500 in words is "six hundred sixty-one billion, one hundred fifty-five million, five hundred fifty-five thousand, five hundred".