644512509 has 96 divisors (see below), whose sum is σ = 1085061120. Its totient is φ = 366436224.

The previous prime is 644512507. The next prime is 644512549. The reversal of 644512509 is 905215446.

644512509 is a `hidden beast` number, since 644 + 5 + 1 + 2 + 5 + 0 + 9 = 666.

It is not a de Polignac number, because 644512509 - 2¹ = 644512507 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644512507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 6257352 + ... + 6257454.

It is an arithmetic number, because the mean of its divisors is an integer number (11302720).

Almost surely, 2^644512509 is an apocalyptic number.

644512509 is a gapful number since it is divisible by the number (69) formed by its first and last digit.

It is an amenable number.

644512509 is a deficient number, since it is larger than the sum of its proper divisors (440548611).

644512509 is a wasteful number, since it uses less digits than its factorization.

644512509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231 (or 228 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

The square root of 644512509 is about 25387.2509145831. The cubic root of 644512509 is about 863.7945314203.

The spelling of 644512509 in words is "six hundred forty-four million, five hundred twelve thousand, five hundred nine".