643866740 has 48 divisors (see below), whose sum is σ = 1476788544. Its totient is φ = 233856000.

The previous prime is 643866719. The next prime is 643866763. The reversal of 643866740 is 47668346.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a junction number, because it is equal to n+sod(n) for n = 643866691 and 643866700.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 318212 + ... + 320228.

It is an arithmetic number, because the mean of its divisors is an integer number (30766428).

Almost surely, 2^643866740 is an apocalyptic number.

It is an amenable number.

643866740 is an abundant number, since it is smaller than the sum of its proper divisors (832921804).

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

643866740 is a wasteful number, since it uses less digits than its factorization.

643866740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3488 (or 3486 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 44.

The square root of 643866740 is about 25374.5293552413. The cubic root of 643866740 is about 863.5059421757.

The spelling of 643866740 in words is "six hundred forty-three million, eight hundred sixty-six thousand, seven hundred forty".