172815635521 has 9 divisors (see below), whose sum is σ = 173771603811. Its totient is φ = 171864904464.

The previous prime is 172815635519. The next prime is 172815635527. The reversal of 172815635521 is 125536518271.

The square root of 172815635521 is 415711.

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., 152286477121 + 20529158400 = 390239^2 + 143280^2 .

It is not a de Polignac number, because 172815635521 - 2¹ = 172815635519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (172815635527) 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, 82725445 + ... + 82727533.

It is an arithmetic number, because the mean of its divisors is an integer number (19307955979).

Almost surely, 2^172815635521 is an apocalyptic number.

172815635521 is the 415711-st square number.

172815635521 is the 207856-th centered octagonal number.

It is an amenable number.

172815635521 is a deficient number, since it is larger than the sum of its proper divisors (955968290).

172815635521 is an frugal number, since it uses more digits than its factorization.

172815635521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4576 (or 2288 counting only the distinct ones).

The product of its digits is 504000, while the sum is 46.

The spelling of 172815635521 in words is "one hundred seventy-two billion, eight hundred fifteen million, six hundred thirty-five thousand, five hundred twenty-one".