644763 has 8 divisors (see below), whose sum is σ = 982528. Its totient is φ = 368424.

The previous prime is 644753. The next prime is 644767. The reversal of 644763 is 367446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644763 - 2⁴ = 644747 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644763.

It is not an unprimeable number, because it can be changed into a prime (644767) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15331 + ... + 15372.

It is an arithmetic number, because the mean of its divisors is an integer number (122816).

2⁶⁴⁴⁷⁶³ is an apocalyptic number.

644763 is a deficient number, since it is larger than the sum of its proper divisors (337765).

644763 is a wasteful number, since it uses less digits than its factorization.

644763 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30713.

The product of its digits is 12096, while the sum is 30.

The square root of 644763 is about 802.9713568989. The cubic root of 644763 is about 86.3906422050.

The spelling of 644763 in words is "six hundred forty-four thousand, seven hundred sixty-three".