644433985 has 32 divisors (see below), whose sum is σ = 849139200. Its totient is φ = 466636800.

The previous prime is 644433973. The next prime is 644433989. The reversal of 644433985 is 589334446.

It is not a de Polignac number, because 644433985 - 2⁷ = 644433857 is a prime.

It is a super-2 number, since 2×644433985² = 830590322045960450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644433989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1435041 + ... + 1435489.

It is an arithmetic number, because the mean of its divisors is an integer number (26535600).

Almost surely, 2^644433985 is an apocalyptic number.

644433985 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

644433985 is a deficient number, since it is larger than the sum of its proper divisors (204705215).

644433985 is a wasteful number, since it uses less digits than its factorization.

644433985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 849.

The product of its digits is 1244160, while the sum is 46.

The square root of 644433985 is about 25385.7043431928. The cubic root of 644433985 is about 863.7594499410.

The spelling of 644433985 in words is "six hundred forty-four million, four hundred thirty-three thousand, nine hundred eighty-five".