172857209121 has 9 divisors (see below), whose sum is σ = 249684437041. Its totient is φ = 115237307892.

The previous prime is 172857209071. The next prime is 172857209143. The reversal of 172857209121 is 121902758271.

The square root of 172857209121 is 415761.

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

172857209121 is a `hidden beast` number, since 1 + 72 + 8 + 572 + 0 + 9 + 1 + 2 + 1 = 666.

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 172857209121 - 2⁹ = 172857208609 is a prime.

It is a super-2 number, since 2×172857209121² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (172857229121) 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, 1177990 + ... + 1316576.

Almost surely, 2^172857209121 is an apocalyptic number.

172857209121 is the 415761-st square number.

172857209121 is the 207881-st centered octagonal number.

It is an amenable number.

172857209121 is a deficient number, since it is larger than the sum of its proper divisors (76827227920).

172857209121 is an frugal number, since it uses more digits than its factorization.

172857209121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 277180 (or 138590 counting only the distinct ones).

The product of its (nonzero) digits is 141120, while the sum is 45.

The spelling of 172857209121 in words is "one hundred seventy-two billion, eight hundred fifty-seven million, two hundred nine thousand, one hundred twenty-one".