656720720 has 20 divisors (see below), whose sum is σ = 1526875860. Its totient is φ = 262688256.

The previous prime is 656720719. The next prime is 656720723. The reversal of 656720720 is 27027656.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 520204864 + 136515856 = 22808^2 + 11684^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656720723) 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, 4104425 + ... + 4104584.

It is an arithmetic number, because the mean of its divisors is an integer number (76343793).

Almost surely, 2^656720720 is an apocalyptic number.

It is an amenable number.

656720720 is an abundant number, since it is smaller than the sum of its proper divisors (870155140).

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

656720720 is a wasteful number, since it uses less digits than its factorization.

656720720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8209022 (or 8209016 counting only the distinct ones).

The product of its (nonzero) digits is 35280, while the sum is 35.

The square root of 656720720 is about 25626.5627816139. The cubic root of 656720720 is about 869.2143874694.

The spelling of 656720720 in words is "six hundred fifty-six million, seven hundred twenty thousand, seven hundred twenty".