644401763 has 4 divisors (see below), whose sum is σ = 644463000. Its totient is φ = 644340528.

The previous prime is 644401759. The next prime is 644401781. The reversal of 644401763 is 367104446.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 644401763 - 2² = 644401759 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644401753) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10370 + ... + 37367.

It is an arithmetic number, because the mean of its divisors is an integer number (161115750).

Almost surely, 2^644401763 is an apocalyptic number.

644401763 is a deficient number, since it is larger than the sum of its proper divisors (61237).

644401763 is a wasteful number, since it uses less digits than its factorization.

644401763 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61236.

The product of its (nonzero) digits is 48384, while the sum is 35.

The square root of 644401763 is about 25385.0696867273. The cubic root of 644401763 is about 863.7450535759.

The spelling of 644401763 in words is "six hundred forty-four million, four hundred one thousand, seven hundred sixty-three".