6991842478866 has 288 divisors, whose sum is σ = 18476106417792. Its totient is φ = 1751975930880.

The previous prime is 6991842478853. The next prime is 6991842478889. The reversal of 6991842478866 is 6688742481996.

It is a super-2 number, since 2×6991842478866² (a number of 26 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 6991842478791 and 6991842478800.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 110029195 + ... + 110092721.

It is an arithmetic number, because the mean of its divisors is an integer number (64153147284).

Almost surely, 2^{6991842478866} is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6991842478866, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (9238053208896).

6991842478866 is an abundant number, since it is smaller than the sum of its proper divisors (11484263938926).

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

6991842478866 is a wasteful number, since it uses less digits than its factorization.

6991842478866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63662 (or 63636 counting only the distinct ones).

The product of its digits is 2006581248, while the sum is 78.

The spelling of 6991842478866 in words is "six trillion, nine hundred ninety-one billion, eight hundred forty-two million, four hundred seventy-eight thousand, eight hundred sixty-six".