172521905 has 4 divisors (see below), whose sum is σ = 207026292. Its totient is φ = 138017520.

The previous prime is 172521901. The next prime is 172521907. The reversal of 172521905 is 509125271.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 103897249 + 68624656 = 10193^2 + 8284^2 .

It is not a de Polignac number, because 172521905 - 2² = 172521901 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (172521901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17252186 + ... + 17252195.

It is an arithmetic number, because the mean of its divisors is an integer number (51756573).

Almost surely, 2^172521905 is an apocalyptic number.

It is an amenable number.

172521905 is a deficient number, since it is larger than the sum of its proper divisors (34504387).

172521905 is an equidigital number, since it uses as much as digits as its factorization.

172521905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34504386.

The product of its (nonzero) digits is 6300, while the sum is 32.

The square root of 172521905 is about 13134.7594191900. The cubic root of 172521905 is about 556.6917026919.

The spelling of 172521905 in words is "one hundred seventy-two million, five hundred twenty-one thousand, nine hundred five".