644386 has 4 divisors (see below), whose sum is σ = 966582. Its totient is φ = 322192.

The previous prime is 644383. The next prime is 644401. The reversal of 644386 is 683446.

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

It can be written as a sum of positive squares in only one way, i.e., 463761 + 180625 = 681^2 + 425^2 .

It is not an unprimeable number, because it can be changed into a prime (644381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161095 + ... + 161098.

2⁶⁴⁴³⁸⁶ is an apocalyptic number.

644386 is a deficient number, since it is larger than the sum of its proper divisors (322196).

644386 is a wasteful number, since it uses less digits than its factorization.

644386 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322195.

The product of its digits is 13824, while the sum is 31.

The square root of 644386 is about 802.7365694921. The cubic root of 644386 is about 86.3738010700.

Subtracting 644386 from its reverse (683446), we obtain a triangular number (39060 = T₂₇₉).

The spelling of 644386 in words is "six hundred forty-four thousand, three hundred eighty-six".