644019 has 4 divisors (see below), whose sum is σ = 858696. Its totient is φ = 429344.

The previous prime is 644009. The next prime is 644029. The reversal of 644019 is 910446.

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

It is an interprime number because it is at equal distance from previous prime (644009) and next prime (644029).

It is a cyclic number.

It is not a de Polignac number, because 644019 - 2⁹ = 643507 is a prime.

It is a super-2 number, since 2×644019² = 829520944722, which contains 22 as substring.

It is a D-number.

It is a self number, because there is not a number n which added to its sum of digits gives 644019.

It is not an unprimeable number, because it can be changed into a prime (644009) 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, 107334 + ... + 107339.

It is an arithmetic number, because the mean of its divisors is an integer number (214674).

2⁶⁴⁴⁰¹⁹ is an apocalyptic number.

644019 is a deficient number, since it is larger than the sum of its proper divisors (214677).

644019 is a wasteful number, since it uses less digits than its factorization.

644019 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214676.

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

The square root of 644019 is about 802.5079438859. The cubic root of 644019 is about 86.3574003388.

The spelling of 644019 in words is "six hundred forty-four thousand, nineteen".