643909540 has 48 divisors (see below), whose sum is σ = 1371142080. Its totient is φ = 253984640.

The previous prime is 643909531. The next prime is 643909549. The reversal of 643909540 is 45909346.

It is an interprime number because it is at equal distance from previous prime (643909531) and next prime (643909549).

It is a junction number, because it is equal to n+sod(n) for n = 643909493 and 643909502.

It is not an unprimeable number, because it can be changed into a prime (643909549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 468294 + ... + 469666.

It is an arithmetic number, because the mean of its divisors is an integer number (28565460).

Almost surely, 2^643909540 is an apocalyptic number.

It is an amenable number.

643909540 is an abundant number, since it is smaller than the sum of its proper divisors (727232540).

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

643909540 is a wasteful number, since it uses less digits than its factorization.

643909540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1692 (or 1690 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 40.

The square root of 643909540 is about 25375.3727066225. The cubic root of 643909540 is about 863.5250751387.

The spelling of 643909540 in words is "six hundred forty-three million, nine hundred nine thousand, five hundred forty".