685234628521 has 27 divisors (see below), whose sum is σ = 708325482199. Its totient is φ = 662893431200.

The previous prime is 685234628513. The next prime is 685234628579. The reversal of 685234628521 is 125826432586.

The square root of 685234628521 is 827789.

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

It can be written as a sum of positive squares in only one way, i.e., 131579582121 + 553655046400 = 362739^2 + 744080^2 .

It is not a de Polignac number, because 685234628521 - 2³ = 685234628513 is a prime.

It is a super-2 number, since 2×685234628521² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (685234628581) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 5230798626 + ... + 5230798756.

Almost surely, 2^685234628521 is an apocalyptic number.

685234628521 is the 827789-th square number.

685234628521 is the 413895-th centered octagonal number.

It is an amenable number.

685234628521 is a deficient number, since it is larger than the sum of its proper divisors (23090853678).

685234628521 is an frugal number, since it uses more digits than its factorization.

685234628521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 582 (or 291 counting only the distinct ones).

The product of its digits is 5529600, while the sum is 52.

The spelling of 685234628521 in words is "six hundred eighty-five billion, two hundred thirty-four million, six hundred twenty-eight thousand, five hundred twenty-one".