644947139 has 12 divisors (see below), whose sum is σ = 686240784. Its totient is φ = 606013824.

The previous prime is 644947129. The next prime is 644947141. The reversal of 644947139 is 931749446.

It is not a de Polignac number, because 644947139 - 2²⁴ = 628169923 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644947093 and 644947102.

It is not an unprimeable number, because it can be changed into a prime (644947109) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 221954 + ... + 224840.

It is an arithmetic number, because the mean of its divisors is an integer number (57186732).

Almost surely, 2^644947139 is an apocalyptic number.

644947139 is a deficient number, since it is larger than the sum of its proper divisors (41293645).

644947139 is a wasteful number, since it uses less digits than its factorization.

644947139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3694 (or 3677 counting only the distinct ones).

The product of its digits is 653184, while the sum is 47.

The square root of 644947139 is about 25395.8094771559. The cubic root of 644947139 is about 863.9886557403.

The spelling of 644947139 in words is "six hundred forty-four million, nine hundred forty-seven thousand, one hundred thirty-nine".