656672051621 has 4 divisors (see below), whose sum is σ = 679315915500. Its totient is φ = 634028187744.

The previous prime is 656672051551. The next prime is 656672051627. The reversal of 656672051621 is 126150276656.

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 308352537025 + 348319514596 = 555295^2 + 590186^2 .

It is a cyclic number.

It is not a de Polignac number, because 656672051621 - 2¹⁰ = 656672050597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656672051627) 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, 11321931896 + ... + 11321931953.

It is an arithmetic number, because the mean of its divisors is an integer number (169828978875).

Almost surely, 2^656672051621 is an apocalyptic number.

It is an amenable number.

656672051621 is a deficient number, since it is larger than the sum of its proper divisors (22643863879).

656672051621 is a wasteful number, since it uses less digits than its factorization.

656672051621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22643863878.

The product of its (nonzero) digits is 907200, while the sum is 47.

The spelling of 656672051621 in words is "six hundred fifty-six billion, six hundred seventy-two million, fifty-one thousand, six hundred twenty-one".