644862 has 16 divisors (see below), whose sum is σ = 1331712. Its totient is φ = 207960.

The previous prime is 644857. The next prime is 644863. The reversal of 644862 is 268446.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644863) by changing a digit.

644862 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, 1548 + ... + 1919.

It is an arithmetic number, because the mean of its divisors is an integer number (83232).

2⁶⁴⁴⁸⁶² is an apocalyptic number.

644862 is a gapful number since it is divisible by the number (62) formed by its first and last digit.

644862 is an abundant number, since it is smaller than the sum of its proper divisors (686850).

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

644862 is a wasteful number, since it uses less digits than its factorization.

644862 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3503.

The product of its digits is 9216, while the sum is 30.

The square root of 644862 is about 803.0330005672. The cubic root of 644862 is about 86.3950635897.

The spelling of 644862 in words is "six hundred forty-four thousand, eight hundred sixty-two".