656991617 has 4 divisors (see below), whose sum is σ = 658455300. Its totient is φ = 655527936.

The previous prime is 656991589. The next prime is 656991623. The reversal of 656991617 is 716199656.

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

It can be written as a sum of positive squares in 2 ways, for example, as 562590961 + 94400656 = 23719^2 + 9716^2 .

It is a cyclic number.

It is not a de Polignac number, because 656991617 - 2⁶ = 656991553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (656991697) 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 3 ways as a sum of consecutive naturals, for example, 731168 + ... + 732065.

It is an arithmetic number, because the mean of its divisors is an integer number (164613825).

Almost surely, 2^656991617 is an apocalyptic number.

It is an amenable number.

656991617 is a deficient number, since it is larger than the sum of its proper divisors (1463683).

656991617 is a wasteful number, since it uses less digits than its factorization.

656991617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1463682.

The product of its digits is 612360, while the sum is 50.

The square root of 656991617 is about 25631.8477094415. The cubic root of 656991617 is about 869.3338878868. Note that the first 3 decimals are identical.

The spelling of 656991617 in words is "six hundred fifty-six million, nine hundred ninety-one thousand, six hundred seventeen".