172121321 has 8 divisors (see below), whose sum is σ = 179212488. Its totient is φ = 165168000.

The previous prime is 172121309. The next prime is 172121353. The reversal of 172121321 is 123121271.

It can be written as a sum of positive squares in 4 ways, for example, as 51912025 + 120209296 = 7205^2 + 10964^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-172121321 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 172121293 and 172121302.

It is not an unprimeable number, because it can be changed into a prime (172127321) 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 7 ways as a sum of consecutive naturals, for example, 31910 + ... + 36911.

It is an arithmetic number, because the mean of its divisors is an integer number (22401561).

Almost surely, 2^172121321 is an apocalyptic number.

It is an amenable number.

172121321 is a deficient number, since it is larger than the sum of its proper divisors (7091167).

172121321 is an equidigital number, since it uses as much as digits as its factorization.

172121321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68923.

The product of its digits is 168, while the sum is 20.

The square root of 172121321 is about 13119.5015530317. The cubic root of 172121321 is about 556.2605021625.

Adding to 172121321 its reverse (123121271), we get a palindrome (295242592).

Subtracting from 172121321 its reverse (123121271), we obtain a triangular number (49000050 = T₉₈₉₉).

The spelling of 172121321 in words is "one hundred seventy-two million, one hundred twenty-one thousand, three hundred twenty-one".