644916 has 24 divisors (see below), whose sum is σ = 1517824. Its totient is φ = 213120.

The previous prime is 644911. The next prime is 644923. The reversal of 644916 is 619446.

644916 = T₁₇₁ + T₁₇₂ + ... + T₂₀₆.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644911) by changing a digit.

644916 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 7 ways as a sum of consecutive naturals, for example, 2556 + ... + 2796.

2⁶⁴⁴⁹¹⁶ is an apocalyptic number.

It is an amenable number.

644916 is an abundant number, since it is smaller than the sum of its proper divisors (872908).

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

644916 is a wasteful number, since it uses less digits than its factorization.

644916 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 471 (or 469 counting only the distinct ones).

The product of its digits is 5184, while the sum is 30.

The square root of 644916 is about 803.0666223919. The cubic root of 644916 is about 86.3974750634.

The spelling of 644916 in words is "six hundred forty-four thousand, nine hundred sixteen".