644638137 has 32 divisors (see below), whose sum is σ = 1062942720. Its totient is φ = 341651520.

The previous prime is 644638109. The next prime is 644638151. The reversal of 644638137 is 731836446.

It is a happy number.

It is not a de Polignac number, because 644638137 - 2⁶ = 644638073 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644638037) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 31393 + ... + 47694.

It is an arithmetic number, because the mean of its divisors is an integer number (33216960).

Almost surely, 2^644638137 is an apocalyptic number.

It is an amenable number.

644638137 is a deficient number, since it is larger than the sum of its proper divisors (418304583).

644638137 is a wasteful number, since it uses less digits than its factorization.

644638137 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79133.

The product of its digits is 290304, while the sum is 42.

The square root of 644638137 is about 25389.7250280502. The cubic root of 644638137 is about 863.8506512152.

The spelling of 644638137 in words is "six hundred forty-four million, six hundred thirty-eight thousand, one hundred thirty-seven".