644901 has 4 divisors (see below), whose sum is σ = 859872. Its totient is φ = 429932.

The previous prime is 644899. The next prime is 644909. The reversal of 644901 is 109446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644901 - 2¹ = 644899 is a prime.

It is a D-number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644909) 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 in 3 ways as a sum of consecutive naturals, for example, 107481 + ... + 107486.

It is an arithmetic number, because the mean of its divisors is an integer number (214968).

2⁶⁴⁴⁹⁰¹ is an apocalyptic number.

It is an amenable number.

644901 is a deficient number, since it is larger than the sum of its proper divisors (214971).

644901 is a wasteful number, since it uses less digits than its factorization.

644901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214970.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 644901 is about 803.0572831374. The cubic root of 644901 is about 86.3968052231.

The spelling of 644901 in words is "six hundred forty-four thousand, nine hundred one".