643996712 has 8 divisors (see below), whose sum is σ = 1207493850. Its totient is φ = 321998352.

The previous prime is 643996709. The next prime is 643996721. The reversal of 643996712 is 217699346.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 374577316 + 269419396 = 19354^2 + 16414^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40249787 + ... + 40249802.

Almost surely, 2^643996712 is an apocalyptic number.

It is an amenable number.

643996712 is a deficient number, since it is larger than the sum of its proper divisors (563497138).

643996712 is a wasteful number, since it uses less digits than its factorization.

643996712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80499595 (or 80499591 counting only the distinct ones).

The product of its digits is 489888, while the sum is 47.

The square root of 643996712 is about 25377.0902981410. The cubic root of 643996712 is about 863.5640411769.

The spelling of 643996712 in words is "six hundred forty-three million, nine hundred ninety-six thousand, seven hundred twelve".