643666420 has 24 divisors (see below), whose sum is σ = 1422842400. Its totient is φ = 243915552.

The previous prime is 643666417. The next prime is 643666433. The reversal of 643666420 is 24666346.

It is a self number, because there is not a number n which added to its sum of digits gives 643666420.

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, 846550 + ... + 847309.

It is an arithmetic number, because the mean of its divisors is an integer number (59285100).

Almost surely, 2^643666420 is an apocalyptic number.

It is an amenable number.

643666420 is an abundant number, since it is smaller than the sum of its proper divisors (779175980).

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

643666420 is a wasteful number, since it uses less digits than its factorization.

643666420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1693887 (or 1693885 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 37.

The square root of 643666420 is about 25370.5817828445. The cubic root of 643666420 is about 863.4163814837.

The spelling of 643666420 in words is "six hundred forty-three million, six hundred sixty-six thousand, four hundred twenty".