661551560656 has 80 divisors (see below), whose sum is σ = 1475732761344. Its totient is φ = 281422282752.

The previous prime is 661551560653. The next prime is 661551560669. The reversal of 661551560656 is 656065155166.

661551560656 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661551560653) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17265936 + ... + 17304208.

Almost surely, 2^661551560656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661551560656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (737866380672).

661551560656 is an abundant number, since it is smaller than the sum of its proper divisors (814181200688).

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

661551560656 is a wasteful number, since it uses less digits than its factorization.

661551560656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39428 (or 39422 counting only the distinct ones).

The product of its (nonzero) digits is 4860000, while the sum is 52.

The spelling of 661551560656 in words is "six hundred sixty-one billion, five hundred fifty-one million, five hundred sixty thousand, six hundred fifty-six".