644024561 has 2 divisors, whose sum is σ = 644024562. Its totient is φ = 644024560.

The previous prime is 644024531. The next prime is 644024593. The reversal of 644024561 is 165420446.

It is an a-pointer prime, because the next prime (644024593) can be obtained adding 644024561 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 438274225 + 205750336 = 20935^2 + 14344^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644024561 is a prime.

It is not a weakly prime, because it can be changed into another prime (644024501) 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, 322012280 + 322012281.

It is an arithmetic number, because the mean of its divisors is an integer number (322012281).

Almost surely, 2^644024561 is an apocalyptic number.

It is an amenable number.

644024561 is a deficient number, since it is larger than the sum of its proper divisors (1).

644024561 is an equidigital number, since it uses as much as digits as its factorization.

644024561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23040, while the sum is 32.

The square root of 644024561 is about 25377.6389957774. The cubic root of 644024561 is about 863.5764889880.

The spelling of 644024561 in words is "six hundred forty-four million, twenty-four thousand, five hundred sixty-one".