661558720 has 112 divisors (see below), whose sum is σ = 1690359840. Its totient is φ = 245846016.

The previous prime is 661558691. The next prime is 661558753. The reversal of 661558720 is 27855166.

661558720 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 321214 + ... + 323266.

Almost surely, 2^661558720 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 661558720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (845179920).

661558720 is an abundant number, since it is smaller than the sum of its proper divisors (1028801120).

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

661558720 is a wasteful number, since it uses less digits than its factorization.

661558720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2142 (or 2132 counting only the distinct ones).

The product of its (nonzero) digits is 100800, while the sum is 40.

The square root of 661558720 is about 25720.7838138732. The cubic root of 661558720 is about 871.3436409723.

The spelling of 661558720 in words is "six hundred sixty-one million, five hundred fifty-eight thousand, seven hundred twenty".