643973964 has 24 divisors (see below), whose sum is σ = 1567937280. Its totient is φ = 205324944.

The previous prime is 643973963. The next prime is 643973969. The reversal of 643973964 is 469379346.

It is a super-3 number, since 3×643973964³ (a number of 27 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (643973963) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1166344 + ... + 1166895.

It is an arithmetic number, because the mean of its divisors is an integer number (65330720).

Almost surely, 2^643973964 is an apocalyptic number.

It is an amenable number.

643973964 is an abundant number, since it is smaller than the sum of its proper divisors (923963316).

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

643973964 is a wasteful number, since it uses less digits than its factorization.

643973964 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2333269 (or 2333267 counting only the distinct ones).

The product of its digits is 2939328, while the sum is 51.

The square root of 643973964 is about 25376.6420946507. The cubic root of 643973964 is about 863.5538731197.

The spelling of 643973964 in words is "six hundred forty-three million, nine hundred seventy-three thousand, nine hundred sixty-four".