172685921 has 2 divisors, whose sum is σ = 172685922. Its totient is φ = 172685920.

The previous prime is 172685879. The next prime is 172685951. The reversal of 172685921 is 129586271.

172685921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 152794321 + 19891600 = 12361^2 + 4460^2 .

It is a cyclic number.

It is not a de Polignac number, because 172685921 - 2²⁶ = 105577057 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (172685951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86342960 + 86342961.

It is an arithmetic number, because the mean of its divisors is an integer number (86342961).

Almost surely, 2^172685921 is an apocalyptic number.

It is an amenable number.

172685921 is a deficient number, since it is larger than the sum of its proper divisors (1).

172685921 is an equidigital number, since it uses as much as digits as its factorization.

172685921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60480, while the sum is 41.

The square root of 172685921 is about 13141.0015219541. The cubic root of 172685921 is about 556.8680617977.

The spelling of 172685921 in words is "one hundred seventy-two million, six hundred eighty-five thousand, nine hundred twenty-one".