644751441 has 16 divisors (see below), whose sum is σ = 962713600. Its totient is φ = 426447504.

The previous prime is 644751439. The next prime is 644751449. The reversal of 644751441 is 144157446.

It is a happy number.

644751441 is a `hidden beast` number, since 64 + 47 + 514 + 41 = 666.

It is not a de Polignac number, because 644751441 - 2¹ = 644751439 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 644751396 and 644751405.

It is not an unprimeable number, because it can be changed into a prime (644751449) 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, 90586 + ... + 97443.

It is an arithmetic number, because the mean of its divisors is an integer number (60169600).

Almost surely, 2^644751441 is an apocalyptic number.

It is an amenable number.

644751441 is a deficient number, since it is larger than the sum of its proper divisors (317962159).

644751441 is a wasteful number, since it uses less digits than its factorization.

644751441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188165 (or 188159 counting only the distinct ones).

The product of its digits is 53760, while the sum is 36.

The square root of 644751441 is about 25391.9562263328. The cubic root of 644751441 is about 863.9012594529.

The spelling of 644751441 in words is "six hundred forty-four million, seven hundred fifty-one thousand, four hundred forty-one".