666661656 has 16 divisors (see below), whose sum is σ = 1666654200. Its totient is φ = 222220544.

The previous prime is 666661651. The next prime is 666661661. The reversal of 666661656 is 656166666.

It is an interprime number because it is at equal distance from previous prime (666661651) and next prime (666661661).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666661651) 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, 13888761 + ... + 13888808.

Almost surely, 2^666661656 is an apocalyptic number.

It is an amenable number.

666661656 is an abundant number, since it is smaller than the sum of its proper divisors (999992544).

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

666661656 is a wasteful number, since it uses less digits than its factorization.

666661656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27777578 (or 27777574 counting only the distinct ones).

The product of its digits is 1399680, while the sum is 48.

The square root of 666661656 is about 25819.7919433910. The cubic root of 666661656 is about 873.5782761206.

The spelling of 666661656 in words is "six hundred sixty-six million, six hundred sixty-one thousand, six hundred fifty-six".