172716821 has 32 divisors (see below), whose sum is σ = 204456960. Its totient is φ = 144688896.

The previous prime is 172716811. The next prime is 172716823. The reversal of 172716821 is 128617271.

172716821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 172716821 - 2²² = 168522517 is a prime.

It is a super-2 number, since 2×172716821² = 59662200512692082, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172716823) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 497570 + ... + 497916.

It is an arithmetic number, because the mean of its divisors is an integer number (6389280).

Almost surely, 2^172716821 is an apocalyptic number.

It is an amenable number.

172716821 is a deficient number, since it is larger than the sum of its proper divisors (31740139).

172716821 is a wasteful number, since it uses less digits than its factorization.

172716821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 473.

The product of its digits is 9408, while the sum is 35.

The square root of 172716821 is about 13142.1771788391. The cubic root of 172716821 is about 556.9012746904.

The spelling of 172716821 in words is "one hundred seventy-two million, seven hundred sixteen thousand, eight hundred twenty-one".