7947978921 has 12 divisors (see below), whose sum is σ = 11530991472. Its totient is φ = 5275309176.

The previous prime is 7947978889. The next prime is 7947978937. The reversal of 7947978921 is 1298797497.

7947978921 is a `hidden beast` number, since 7 + 9 + 479 + 78 + 92 + 1 = 666.

It is not a de Polignac number, because 7947978921 - 2⁵ = 7947978889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (7947978721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1943131 + ... + 1947216.

It is an arithmetic number, because the mean of its divisors is an integer number (960915956).

Almost surely, 2^7947978921 is an apocalyptic number.

It is an amenable number.

7947978921 is a deficient number, since it is larger than the sum of its proper divisors (3583012551).

7947978921 is a wasteful number, since it uses less digits than its factorization.

7947978921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3890580 (or 3890577 counting only the distinct ones).

The product of its digits is 16003008, while the sum is 63.

The square root of 7947978921 is about 89151.4381319786. The cubic root of 7947978921 is about 1995.6554794876.

The spelling of 7947978921 in words is "seven billion, nine hundred forty-seven million, nine hundred seventy-eight thousand, nine hundred twenty-one".