644494 has 4 divisors (see below), whose sum is σ = 966744. Its totient is φ = 322246.

The previous prime is 644491. The next prime is 644507. The reversal of 644494 is 494446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 494446 = 2 ⋅247223.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644491) 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 as a sum of consecutive naturals, namely, 161122 + ... + 161125.

It is an arithmetic number, because the mean of its divisors is an integer number (241686).

2⁶⁴⁴⁴⁹⁴ is an apocalyptic number.

644494 is a deficient number, since it is larger than the sum of its proper divisors (322250).

644494 is a wasteful number, since it uses less digits than its factorization.

644494 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322249.

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

The square root of 644494 is about 802.8038365628. The cubic root of 644494 is about 86.3786262573.

The spelling of 644494 in words is "six hundred forty-four thousand, four hundred ninety-four".