645805873 has 2 divisors, whose sum is σ = 645805874. Its totient is φ = 645805872.

The previous prime is 645805789. The next prime is 645805903. The reversal of 645805873 is 378508546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 322992784 + 322813089 = 17972^2 + 17967^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645805873 is a prime.

It is not a weakly prime, because it can be changed into another prime (645805273) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322902936 + 322902937.

It is an arithmetic number, because the mean of its divisors is an integer number (322902937).

Almost surely, 2^645805873 is an apocalyptic number.

It is an amenable number.

645805873 is a deficient number, since it is larger than the sum of its proper divisors (1).

645805873 is an equidigital number, since it uses as much as digits as its factorization.

645805873 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 806400, while the sum is 46.

The square root of 645805873 is about 25412.7108550032. The cubic root of 645805873 is about 864.3719467842.

The spelling of 645805873 in words is "six hundred forty-five million, eight hundred five thousand, eight hundred seventy-three".