644726833 has 2 divisors, whose sum is σ = 644726834. Its totient is φ = 644726832.

The previous prime is 644726827. The next prime is 644726837. The reversal of 644726833 is 338627446.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 539725824 + 105001009 = 23232^2 + 10247^2 .

It is a cyclic number.

It is not a de Polignac number, because 644726833 - 2²⁹ = 107855921 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644726833.

It is not a weakly prime, because it can be changed into another prime (644726837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322363416 + 322363417.

It is an arithmetic number, because the mean of its divisors is an integer number (322363417).

Almost surely, 2^644726833 is an apocalyptic number.

It is an amenable number.

644726833 is a deficient number, since it is larger than the sum of its proper divisors (1).

644726833 is an equidigital number, since it uses as much as digits as its factorization.

644726833 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 580608, while the sum is 43.

The square root of 644726833 is about 25391.4716588070. The cubic root of 644726833 is about 863.8902685753.

The spelling of 644726833 in words is "six hundred forty-four million, seven hundred twenty-six thousand, eight hundred thirty-three".