656487668681 has 8 divisors (see below), whose sum is σ = 707009722440. Its totient is φ = 605968900992.

The previous prime is 656487668677. The next prime is 656487668687. The reversal of 656487668681 is 186866784656.

It can be written as a sum of positive squares in 4 ways, for example, as 408204710281 + 248282958400 = 638909^2 + 498280^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 656487668681 - 2² = 656487668677 is a prime.

It is a super-2 number, since 2×656487668681² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (656487668687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 398516 + ... + 1213173.

It is an arithmetic number, because the mean of its divisors is an integer number (88376215305).

Almost surely, 2^656487668681 is an apocalyptic number.

It is an amenable number.

656487668681 is a deficient number, since it is larger than the sum of its proper divisors (50522053759).

656487668681 is a wasteful number, since it uses less digits than its factorization.

656487668681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1643035.

The product of its digits is 557383680, while the sum is 71.

The spelling of 656487668681 in words is "six hundred fifty-six billion, four hundred eighty-seven million, six hundred sixty-eight thousand, six hundred eighty-one".