644836869 has 20 divisors (see below), whose sum is σ = 965394144. Its totient is φ = 428945544.

The previous prime is 644836867. The next prime is 644836883. The reversal of 644836869 is 968638446.

It is not a de Polignac number, because 644836869 - 2¹ = 644836867 is a prime.

It is a super-2 number, since 2×644836869² = 831629175243446322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644836861) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 29304 + ... + 46350.

Almost surely, 2^644836869 is an apocalyptic number.

It is an amenable number.

644836869 is a deficient number, since it is larger than the sum of its proper divisors (320557275).

644836869 is a wasteful number, since it uses less digits than its factorization.

644836869 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17526 (or 17517 counting only the distinct ones).

The product of its digits is 5971968, while the sum is 54.

The square root of 644836869 is about 25393.6383568799. The cubic root of 644836869 is about 863.9394127075.

The spelling of 644836869 in words is "six hundred forty-four million, eight hundred thirty-six thousand, eight hundred sixty-nine".