656728781 has 4 divisors (see below), whose sum is σ = 657228000. Its totient is φ = 656229564.

The previous prime is 656728759. The next prime is 656728783. The reversal of 656728781 is 187827656.

656728781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 656728781 - 2²⁶ = 589619917 is a prime.

It is a super-2 number, since 2×656728781² = 862585383587491922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656728783) 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, 247631 + ... + 250268.

It is an arithmetic number, because the mean of its divisors is an integer number (164307000).

Almost surely, 2^656728781 is an apocalyptic number.

It is an amenable number.

656728781 is a deficient number, since it is larger than the sum of its proper divisors (499219).

656728781 is a wasteful number, since it uses less digits than its factorization.

656728781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499218.

The product of its digits is 1128960, while the sum is 50.

The square root of 656728781 is about 25626.7200593443. The cubic root of 656728781 is about 869.2179438814.

The spelling of 656728781 in words is "six hundred fifty-six million, seven hundred twenty-eight thousand, seven hundred eighty-one".