644406 has 32 divisors (see below), whose sum is σ = 1501440. Its totient is φ = 180576.

The previous prime is 644401. The next prime is 644411. The reversal of 644406 is 604446.

It is an interprime number because it is at equal distance from previous prime (644401) and next prime (644411).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2700 + ... + 2928.

It is an arithmetic number, because the mean of its divisors is an integer number (46920).

2⁶⁴⁴⁴⁰⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644406, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (750720).

644406 is an abundant number, since it is smaller than the sum of its proper divisors (857034).

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

644406 is a wasteful number, since it uses less digits than its factorization.

644406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 308.

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 644406 is about 802.7490267823. The cubic root of 644406 is about 86.3746946639.

It can be divided in two parts, 64440 and 6, that added together give a palindrome (64446).

The spelling of 644406 in words is "six hundred forty-four thousand, four hundred six".