644690533 has 2 divisors, whose sum is σ = 644690534. Its totient is φ = 644690532.

The previous prime is 644690509. The next prime is 644690597. The reversal of 644690533 is 335096446.

644690533 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 535320769 + 109369764 = 23137^2 + 10458^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644690533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644690633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322345266 + 322345267.

It is an arithmetic number, because the mean of its divisors is an integer number (322345267).

Almost surely, 2^644690533 is an apocalyptic number.

It is an amenable number.

644690533 is a deficient number, since it is larger than the sum of its proper divisors (1).

644690533 is an equidigital number, since it uses as much as digits as its factorization.

644690533 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 233280, while the sum is 40.

The square root of 644690533 is about 25390.7568418115. The cubic root of 644690533 is about 863.8740550909.

The spelling of 644690533 in words is "six hundred forty-four million, six hundred ninety thousand, five hundred thirty-three".