172018921 has 2 divisors, whose sum is σ = 172018922. Its totient is φ = 172018920.

The previous prime is 172018897. The next prime is 172018943. The reversal of 172018921 is 129810271.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 167443600 + 4575321 = 12940^2 + 2139^2 .

It is a cyclic number.

It is not a de Polignac number, because 172018921 - 2⁷ = 172018793 is a prime.

It is not a weakly prime, because it can be changed into another prime (172018991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86009460 + 86009461.

It is an arithmetic number, because the mean of its divisors is an integer number (86009461).

Almost surely, 2^172018921 is an apocalyptic number.

It is an amenable number.

172018921 is a deficient number, since it is larger than the sum of its proper divisors (1).

172018921 is an equidigital number, since it uses as much as digits as its factorization.

172018921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 31.

The square root of 172018921 is about 13115.5983851291. The cubic root of 172018921 is about 556.1501684073.

The spelling of 172018921 in words is "one hundred seventy-two million, eighteen thousand, nine hundred twenty-one".