172928221 has 2 divisors, whose sum is σ = 172928222. Its totient is φ = 172928220.

The previous prime is 172928213. The next prime is 172928227. The reversal of 172928221 is 122829271.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 172265625 + 662596 = 13125^2 + 814^2 .

It is a cyclic number.

It is not a de Polignac number, because 172928221 - 2³ = 172928213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (172928227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86464110 + 86464111.

It is an arithmetic number, because the mean of its divisors is an integer number (86464111).

Almost surely, 2^172928221 is an apocalyptic number.

It is an amenable number.

172928221 is a deficient number, since it is larger than the sum of its proper divisors (1).

172928221 is an equidigital number, since it uses as much as digits as its factorization.

172928221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8064, while the sum is 34.

The square root of 172928221 is about 13150.2175267180. The cubic root of 172928221 is about 557.1283919822.

The spelling of 172928221 in words is "one hundred seventy-two million, nine hundred twenty-eight thousand, two hundred twenty-one".