6646978866 has 16 divisors (see below), whose sum is σ = 14502499488. Its totient is φ = 2014236000.

The previous prime is 6646978859. The next prime is 6646978913. The reversal of 6646978866 is 6688796466.

It is a Harshad number since it is a multiple of its sum of digits (66), and also a Moran number because the ratio is a prime number: 100711801 = 6646978866 / (6 + 6 + 4 + 6 + 9 + 7 + 8 + 8 + 6 + 6).

It is a junction number, because it is equal to n+sod(n) for n = 6646978797 and 6646978806.

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, 50355835 + ... + 50355966.

It is an arithmetic number, because the mean of its divisors is an integer number (906406218).

Almost surely, 2^6646978866 is an apocalyptic number.

6646978866 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

6646978866 is an abundant number, since it is smaller than the sum of its proper divisors (7855520622).

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

6646978866 is a wasteful number, since it uses less digits than its factorization.

6646978866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100711817.

The product of its digits is 125411328, while the sum is 66.

The square root of 6646978866 is about 81529.0062861065. The cubic root of 6646978866 is about 1880.2175380158.

The spelling of 6646978866 in words is "six billion, six hundred forty-six million, nine hundred seventy-eight thousand, eight hundred sixty-six".