644144399 has 16 divisors (see below), whose sum is σ = 700267680. Its totient is φ = 590115840.

The previous prime is 644144377. The next prime is 644144401. The reversal of 644144399 is 993441446.

It is a Cunningham number, because it is equal to 25380²-1.

It is a cyclic number.

It is not a de Polignac number, because 644144399 - 2²⁰ = 643095823 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644144309) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 430697 + ... + 432189.

It is an arithmetic number, because the mean of its divisors is an integer number (43766730).

Almost surely, 2^644144399 is an apocalyptic number.

644144399 is a deficient number, since it is larger than the sum of its proper divisors (56123281).

644144399 is a wasteful number, since it uses less digits than its factorization.

644144399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2170.

The product of its digits is 373248, while the sum is 44.

The square root of 644144399 is about 25379.9999802994. Note that the first 4 decimals coincide. The cubic root of 644144399 is about 863.6300495027.

The spelling of 644144399 in words is "six hundred forty-four million, one hundred forty-four thousand, three hundred ninety-nine".