172156221 has 12 divisors (see below), whose sum is σ = 248901120. Its totient is φ = 114664200.

The previous prime is 172156189. The next prime is 172156249. The reversal of 172156221 is 122651271.

172156221 is a `hidden beast` number, since 17 + 21 + 5 + 622 + 1 = 666.

172156221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 172156221 - 2⁵ = 172156189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172156261) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2050 + ... + 18668.

It is an arithmetic number, because the mean of its divisors is an integer number (20741760).

Almost surely, 2^172156221 is an apocalyptic number.

It is an amenable number.

172156221 is a deficient number, since it is larger than the sum of its proper divisors (76744899).

172156221 is a wasteful number, since it uses less digits than its factorization.

172156221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17776 (or 17773 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 172156221 is about 13120.8315666348. The cubic root of 172156221 is about 556.2980961484.

It can be divided in two parts, 17215 and 6221, that added together give a triangular number (23436 = T₂₁₆).

The spelling of 172156221 in words is "one hundred seventy-two million, one hundred fifty-six thousand, two hundred twenty-one".