644136686631447 has 32 divisors (see below), whose sum is σ = 897751133775360. Its totient is φ = 410287390800000.

The previous prime is 644136686631413. The next prime is 644136686631457. The reversal of 644136686631447 is 744136686631446.

It is not a de Polignac number, because 644136686631447 - 2¹¹ = 644136686629399 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644136686631457) 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, 3928929 + ... + 36106922.

It is an arithmetic number, because the mean of its divisors is an integer number (28054722930480).

Almost surely, 2^{644136686631447} is an apocalyptic number.

644136686631447 is a deficient number, since it is larger than the sum of its proper divisors (253614447143913).

644136686631447 is a wasteful number, since it uses less digits than its factorization.

644136686631447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40037815.

The product of its digits is 1003290624, while the sum is 69.

Subtracting 644136686631447 from its reverse (744136686631446), we obtain a palindrome (99999999999999).

The spelling of 644136686631447 in words is "six hundred forty-four trillion, one hundred thirty-six billion, six hundred eighty-six million, six hundred thirty-one thousand, four hundred forty-seven".