172172021 has 4 divisors (see below), whose sum is σ = 196768032. Its totient is φ = 147576012.

The previous prime is 172172017. The next prime is 172172023. The reversal of 172172021 is 120271271.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 120271271 = 701 ⋅171571.

It is a cyclic number.

It is not a de Polignac number, because 172172021 - 2² = 172172017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172172023) 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, 12297995 + ... + 12298008.

It is an arithmetic number, because the mean of its divisors is an integer number (49192008).

Almost surely, 2^172172021 is an apocalyptic number.

It is an amenable number.

172172021 is a deficient number, since it is larger than the sum of its proper divisors (24596011).

172172021 is an equidigital number, since it uses as much as digits as its factorization.

172172021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24596010.

The product of its (nonzero) digits is 392, while the sum is 23.

The square root of 172172021 is about 13121.4336488053. The cubic root of 172172021 is about 556.3151141046.

The spelling of 172172021 in words is "one hundred seventy-two million, one hundred seventy-two thousand, twenty-one".