661552218 has 16 divisors (see below), whose sum is σ = 1470116160. Its totient is φ = 220517388.

The previous prime is 661552189. The next prime is 661552223. The reversal of 661552218 is 812255166.

661552218 is a `hidden beast` number, since 6 + 615 + 5 + 22 + 18 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6125430 + ... + 6125537.

It is an arithmetic number, because the mean of its divisors is an integer number (91882260).

Almost surely, 2^661552218 is an apocalyptic number.

661552218 is an abundant number, since it is smaller than the sum of its proper divisors (808563942).

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

661552218 is a wasteful number, since it uses less digits than its factorization.

661552218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12250978 (or 12250972 counting only the distinct ones).

The product of its digits is 28800, while the sum is 36.

The square root of 661552218 is about 25720.6574177255. The cubic root of 661552218 is about 871.3407863530.

The spelling of 661552218 in words is "six hundred sixty-one million, five hundred fifty-two thousand, two hundred eighteen".