644142749 has 2 divisors, whose sum is σ = 644142750. Its totient is φ = 644142748.

The previous prime is 644142727. The next prime is 644142773. The reversal of 644142749 is 947241446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 611572900 + 32569849 = 24730^2 + 5707^2 .

It is a cyclic number.

It is not a de Polignac number, because 644142749 - 2²⁴ = 627365533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644142449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322071374 + 322071375.

It is an arithmetic number, because the mean of its divisors is an integer number (322071375).

Almost surely, 2^644142749 is an apocalyptic number.

It is an amenable number.

644142749 is a deficient number, since it is larger than the sum of its proper divisors (1).

644142749 is an equidigital number, since it uses as much as digits as its factorization.

644142749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 41.

The square root of 644142749 is about 25379.9674743684. The cubic root of 644142749 is about 863.6293120952.

The spelling of 644142749 in words is "six hundred forty-four million, one hundred forty-two thousand, seven hundred forty-nine".