657171256921 has 9 divisors (see below), whose sum is σ = 665252489461. Its totient is φ = 649187056732.

The previous prime is 657171256897. The next prime is 657171256927. The reversal of 657171256921 is 129652171756.

The square root of 657171256921 is 810661.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 657171256921 - 2²¹ = 657169159769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (657171256927) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 67279980 + ... + 67289746.

Almost surely, 2^657171256921 is an apocalyptic number.

657171256921 is the 810661-st square number.

657171256921 is the 405331-st centered octagonal number.

It is an amenable number.

657171256921 is a deficient number, since it is larger than the sum of its proper divisors (8081232540).

657171256921 is an frugal number, since it uses more digits than its factorization.

657171256921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19700 (or 9850 counting only the distinct ones).

The product of its digits is 1587600, while the sum is 52.

The spelling of 657171256921 in words is "six hundred fifty-seven billion, one hundred seventy-one million, two hundred fifty-six thousand, nine hundred twenty-one".