644136020 has 24 divisors (see below), whose sum is σ = 1475657568. Its totient is φ = 234231200.

The previous prime is 644136007. The next prime is 644136049. The reversal of 644136020 is 20631446.

It is a super-2 number, since 2×644136020² = 829822424522880800, which contains 22 as substring.

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1463726 + ... + 1464165.

It is an arithmetic number, because the mean of its divisors is an integer number (61485732).

Almost surely, 2^644136020 is an apocalyptic number.

It is an amenable number.

644136020 is an abundant number, since it is smaller than the sum of its proper divisors (831521548).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644136020 is a wasteful number, since it uses less digits than its factorization.

644136020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2927911 (or 2927909 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 26.

The square root of 644136020 is about 25379.8349088405. The cubic root of 644136020 is about 863.6263048002.

Adding to 644136020 its reverse (20631446), we get a palindrome (664767466).

The spelling of 644136020 in words is "six hundred forty-four million, one hundred thirty-six thousand, twenty".