6991978644 has 120 divisors (see below), whose sum is σ = 21989204160. Its totient is φ = 1892553984.

The previous prime is 6991978627. The next prime is 6991978657. The reversal of 6991978644 is 4468791996.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 38037 + ... + 124220.

It is an arithmetic number, because the mean of its divisors is an integer number (183243368).

Almost surely, 2^6991978644 is an apocalyptic number.

It is an amenable number.

6991978644 is an abundant number, since it is smaller than the sum of its proper divisors (14997225516).

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

6991978644 is a wasteful number, since it uses less digits than its factorization.

6991978644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162299 (or 162288 counting only the distinct ones).

The product of its digits is 23514624, while the sum is 63.

The square root of 6991978644 is about 83618.0521418671. The cubic root of 6991978644 is about 1912.2002224482.

The spelling of 6991978644 in words is "six billion, nine hundred ninety-one million, nine hundred seventy-eight thousand, six hundred forty-four".