645123173 has 2 divisors, whose sum is σ = 645123174. Its totient is φ = 645123172.

The previous prime is 645123163. The next prime is 645123179. The reversal of 645123173 is 371321546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 481231969 + 163891204 = 21937^2 + 12802^2 .

It is a cyclic number.

It is not a de Polignac number, because 645123173 - 2²⁶ = 578014309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645123179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322561586 + 322561587.

It is an arithmetic number, because the mean of its divisors is an integer number (322561587).

Almost surely, 2^645123173 is an apocalyptic number.

It is an amenable number.

645123173 is a deficient number, since it is larger than the sum of its proper divisors (1).

645123173 is an equidigital number, since it uses as much as digits as its factorization.

645123173 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15120, while the sum is 32.

The square root of 645123173 is about 25399.2750487096. The cubic root of 645123173 is about 864.0672552277.

The spelling of 645123173 in words is "six hundred forty-five million, one hundred twenty-three thousand, one hundred seventy-three".