644425211 has 4 divisors (see below), whose sum is σ = 666646800. Its totient is φ = 622203624.

The previous prime is 644425207. The next prime is 644425231. The reversal of 644425211 is 112524446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644425211 - 2² = 644425207 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 22221559 = 644425211 / (6 + 4 + 4 + 4 + 2 + 5 + 2 + 1 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644425231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11110751 + ... + 11110808.

It is an arithmetic number, because the mean of its divisors is an integer number (166661700).

Almost surely, 2^644425211 is an apocalyptic number.

644425211 is a deficient number, since it is larger than the sum of its proper divisors (22221589).

644425211 is a wasteful number, since it uses less digits than its factorization.

644425211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22221588.

The product of its digits is 7680, while the sum is 29.

The square root of 644425211 is about 25385.5315288059. The cubic root of 644425211 is about 863.7555298810.

Adding to 644425211 its reverse (112524446), we get a palindrome (756949657).

The spelling of 644425211 in words is "six hundred forty-four million, four hundred twenty-five thousand, two hundred eleven".