644005407 has 48 divisors (see below), whose sum is σ = 964625760. Its totient is φ = 380362752.

The previous prime is 644005403. The next prime is 644005423. The reversal of 644005407 is 704500446.

It is not a de Polignac number, because 644005407 - 2² = 644005403 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644005403) 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 47 ways as a sum of consecutive naturals, for example, 6639183 + ... + 6639279.

It is an arithmetic number, because the mean of its divisors is an integer number (20096370).

Almost surely, 2^644005407 is an apocalyptic number.

644005407 is a gapful number since it is divisible by the number (67) formed by its first and last digit.

644005407 is a deficient number, since it is larger than the sum of its proper divisors (320620353).

644005407 is a wasteful number, since it uses less digits than its factorization.

644005407 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280 (or 213 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 30.

The square root of 644005407 is about 25377.2616134996. The cubic root of 644005407 is about 863.5679276644.

The spelling of 644005407 in words is "six hundred forty-four million, five thousand, four hundred seven".