644533 has 4 divisors (see below), whose sum is σ = 656748. Its totient is φ = 632320.

The previous prime is 644531. The next prime is 644549. The reversal of 644533 is 335446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 305809 + 338724 = 553^2 + 582^2 .

It is a cyclic number.

It is not a de Polignac number, because 644533 - 2¹ = 644531 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644498 and 644507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6028 + ... + 6133.

It is an arithmetic number, because the mean of its divisors is an integer number (164187).

2⁶⁴⁴⁵³³ is an apocalyptic number.

It is an amenable number.

644533 is a deficient number, since it is larger than the sum of its proper divisors (12215).

644533 is a wasteful number, since it uses less digits than its factorization.

644533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12214.

The product of its digits is 4320, while the sum is 25.

The square root of 644533 is about 802.8281260644. The cubic root of 644533 is about 86.3803685536.

Adding to 644533 its reverse (335446), we get a palindrome (979979).

The spelling of 644533 in words is "six hundred forty-four thousand, five hundred thirty-three".