656573981 has 6 divisors (see below), whose sum is σ = 763769790. Its totient is φ = 562777656.

The previous prime is 656573963. The next prime is 656573987. The reversal of 656573981 is 189375656.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 630461881 + 26112100 = 25109^2 + 5110^2 .

It is a de Polignac number, because none of the positive numbers 2^k-656573981 is a prime.

It is a super-2 number, since 2×656573981² = 862178785052376722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656573987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6699686 + ... + 6699783.

It is an arithmetic number, because the mean of its divisors is an integer number (127294965).

Almost surely, 2^656573981 is an apocalyptic number.

It is an amenable number.

656573981 is a deficient number, since it is larger than the sum of its proper divisors (107195809).

656573981 is a wasteful number, since it uses less digits than its factorization.

656573981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13399483 (or 13399476 counting only the distinct ones).

The product of its digits is 1360800, while the sum is 50.

The square root of 656573981 is about 25623.6995962722. The cubic root of 656573981 is about 869.1496429759.

The spelling of 656573981 in words is "six hundred fifty-six million, five hundred seventy-three thousand, nine hundred eighty-one".