644742 has 72 divisors (see below), whose sum is σ = 1760616. Its totient is φ = 169344.

The previous prime is 644731. The next prime is 644747. The reversal of 644742 is 247446.

644742 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644747) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 14973 + ... + 15015.

It is an arithmetic number, because the mean of its divisors is an integer number (24453).

2⁶⁴⁴⁷⁴² is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644742, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (880308).

644742 is an abundant number, since it is smaller than the sum of its proper divisors (1115874).

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

644742 is a wasteful number, since it uses less digits than its factorization.

644742 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82 (or 72 counting only the distinct ones).

The product of its digits is 5376, while the sum is 27.

The square root of 644742 is about 802.9582803608. The cubic root of 644742 is about 86.3897042773.

The spelling of 644742 in words is "six hundred forty-four thousand, seven hundred forty-two".