644826 has 32 divisors (see below), whose sum is σ = 1588608. Its totient is φ = 169920.

The previous prime is 644801. The next prime is 644837. The reversal of 644826 is 628446.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 644793 and 644802.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644826.

It is an unprimeable number.

644826 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 15 ways as a sum of consecutive naturals, for example, 45 + ... + 1136.

It is an arithmetic number, because the mean of its divisors is an integer number (49644).

2⁶⁴⁴⁸²⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644826, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (794304).

644826 is an abundant number, since it is smaller than the sum of its proper divisors (943782).

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

644826 is a wasteful number, since it uses less digits than its factorization.

644826 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1206.

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

The square root of 644826 is about 803.0105852353. The cubic root of 644826 is about 86.3934558658.

The spelling of 644826 in words is "six hundred forty-four thousand, eight hundred twenty-six".