644666447 has 16 divisors (see below), whose sum is σ = 685393920. Its totient is φ = 604656000.

The previous prime is 644666443. The next prime is 644666459. The reversal of 644666447 is 744666446.

It is not a de Polignac number, because 644666447 - 2² = 644666443 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 (644666443) 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, 1455008 + ... + 1455450.

It is an arithmetic number, because the mean of its divisors is an integer number (42837120).

Almost surely, 2^644666447 is an apocalyptic number.

644666447 is a deficient number, since it is larger than the sum of its proper divisors (40727473).

644666447 is a wasteful number, since it uses less digits than its factorization.

644666447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1054.

The product of its digits is 2322432, while the sum is 47.

The square root of 644666447 is about 25390.2825309212. The cubic root of 644666447 is about 863.8632966838.

Subtracting 644666447 from its reverse (744666446), we obtain a palindrome (99999999).

The spelling of 644666447 in words is "six hundred forty-four million, six hundred sixty-six thousand, four hundred forty-seven".