645744 has 40 divisors (see below), whose sum is σ = 1821312. Its totient is φ = 195520.

The previous prime is 645739. The next prime is 645751. The reversal of 645744 is 447546.

645744 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

645744 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, 84 + ... + 1139.

2⁶⁴⁵⁷⁴⁴ 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 645744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (910656).

645744 is an abundant number, since it is smaller than the sum of its proper divisors (1175568).

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

645744 is a wasteful number, since it uses less digits than its factorization.

645744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1245 (or 1239 counting only the distinct ones).

The product of its digits is 13440, while the sum is 30.

The square root of 645744 is about 803.5819808831. The cubic root of 645744 is about 86.4344341485.

The spelling of 645744 in words is "six hundred forty-five thousand, seven hundred forty-four".