6643878866 has 8 divisors (see below), whose sum is σ = 10208887164. Its totient is φ = 3240916480.

The previous prime is 6643878811. The next prime is 6643878869. The reversal of 6643878866 is 6688783466.

It can be written as a sum of positive squares in 2 ways, for example, as 6452748241 + 191130625 = 80329^2 + 13825^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×6643878866² = 88282252772162891912, which contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 6643878799 and 6643878808.

It is not an unprimeable number, because it can be changed into a prime (6643878869) 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 3 ways as a sum of consecutive naturals, for example, 40511375 + ... + 40511538.

Almost surely, 2^6643878866 is an apocalyptic number.

6643878866 is a deficient number, since it is larger than the sum of its proper divisors (3565008298).

6643878866 is a wasteful number, since it uses less digits than its factorization.

6643878866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81022956.

The product of its digits is 55738368, while the sum is 62.

The square root of 6643878866 is about 81509.9924303763. The cubic root of 6643878866 is about 1879.9251956429.

The spelling of 6643878866 in words is "six billion, six hundred forty-three million, eight hundred seventy-eight thousand, eight hundred sixty-six".