644776 has 32 divisors (see below), whose sum is σ = 1399680. Its totient is φ = 275200.

The previous prime is 644767. The next prime is 644783. The reversal of 644776 is 677446.

644776 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is an unprimeable number.

644776 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1281 + ... + 1711.

It is an arithmetic number, because the mean of its divisors is an integer number (43740).

2⁶⁴⁴⁷⁷⁶ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (699840).

644776 is an abundant number, since it is smaller than the sum of its proper divisors (754904).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644776 is a wasteful number, since it uses less digits than its factorization.

644776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 465 (or 461 counting only the distinct ones).

The product of its digits is 28224, while the sum is 34.

The square root of 644776 is about 802.9794517919. The cubic root of 644776 is about 86.3912228167.

The spelling of 644776 in words is "six hundred forty-four thousand, seven hundred seventy-six".