645929021 has 2 divisors, whose sum is σ = 645929022. Its totient is φ = 645929020.

The previous prime is 645929003. The next prime is 645929029. The reversal of 645929021 is 120929546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 403005625 + 242923396 = 20075^2 + 15586^2 .

It is a cyclic number.

It is not a de Polignac number, because 645929021 - 2²⁶ = 578820157 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645929029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322964510 + 322964511.

It is an arithmetic number, because the mean of its divisors is an integer number (322964511).

Almost surely, 2^645929021 is an apocalyptic number.

It is an amenable number.

645929021 is a deficient number, since it is larger than the sum of its proper divisors (1).

645929021 is an equidigital number, since it uses as much as digits as its factorization.

645929021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 645929021 is about 25415.1337002189. The cubic root of 645929021 is about 864.4268853324.

The spelling of 645929021 in words is "six hundred forty-five million, nine hundred twenty-nine thousand, twenty-one".