656981971138 has 4 divisors (see below), whose sum is σ = 985472956710. Its totient is φ = 328490985568.

The previous prime is 656981971103. The next prime is 656981971153. The reversal of 656981971138 is 831179189656.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 644579362449 + 12402608689 = 802857^2 + 111367^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 656981971138.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 164245492783 + ... + 164245492786.

Almost surely, 2^656981971138 is an apocalyptic number.

656981971138 is a deficient number, since it is larger than the sum of its proper divisors (328490985572).

656981971138 is a wasteful number, since it uses less digits than its factorization.

656981971138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328490985571.

The product of its digits is 19595520, while the sum is 64.

The spelling of 656981971138 in words is "six hundred fifty-six billion, nine hundred eighty-one million, nine hundred seventy-one thousand, one hundred thirty-eight".