643839840 has 480 divisors, whose sum is σ = 2669635584. Its totient is φ = 143078400.

The previous prime is 643839839. The next prime is 643839853. The reversal of 643839840 is 48938346.

It is a tau number, because it is divible by the number of its divisors (480).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 4263765 + ... + 4263915.

Almost surely, 2^643839840 is an apocalyptic number.

643839840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643839840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1334817792).

643839840 is an abundant number, since it is smaller than the sum of its proper divisors (2025795744).

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

643839840 is a wasteful number, since it uses less digits than its factorization.

643839840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 232 (or 215 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 45.

The square root of 643839840 is about 25373.9992906124. Note that the first 3 decimals coincide. The cubic root of 643839840 is about 863.4939165852.

The spelling of 643839840 in words is "six hundred forty-three million, eight hundred thirty-nine thousand, eight hundred forty".