644356 has 12 divisors (see below), whose sum is σ = 1155420. Its totient is φ = 314240.

The previous prime is 644353. The next prime is 644359. The reversal of 644356 is 653446.

It is an interprime number because it is at equal distance from previous prime (644353) and next prime (644359).

It can be written as a sum of positive squares in 2 ways, for example, as 57600 + 586756 = 240^2 + 766^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644353) 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, 1801 + ... + 2128.

It is an arithmetic number, because the mean of its divisors is an integer number (96285).

2⁶⁴⁴³⁵⁶ is an apocalyptic number.

It is an amenable number.

644356 is a deficient number, since it is larger than the sum of its proper divisors (511064).

644356 is a wasteful number, since it uses less digits than its factorization.

644356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3974 (or 3972 counting only the distinct ones).

The product of its digits is 8640, while the sum is 28.

The square root of 644356 is about 802.7178831943. The cubic root of 644356 is about 86.3724606446.

It can be divided in two parts, 644 and 356, that added together give a cube (1000 = 10³).

The spelling of 644356 in words is "six hundred forty-four thousand, three hundred fifty-six".