9791221978 has 16 divisors (see below), whose sum is σ = 15563649960. Its totient is φ = 4603815936.

The previous prime is 9791221861. The next prime is 9791222027. The reversal of 9791221978 is 8791221979.

It can be written as a sum of positive squares in 4 ways, for example, as 5968644049 + 3822577929 = 77257^2 + 61827^2 .

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, 77463 + ... + 159946.

Almost surely, 2^9791221978 is an apocalyptic number.

9791221978 is a deficient number, since it is larger than the sum of its proper divisors (5772427982).

9791221978 is a wasteful number, since it uses less digits than its factorization.

9791221978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238641.

The product of its digits is 1143072, while the sum is 55.

The square root of 9791221978 is about 98950.6037273144. The cubic root of 9791221978 is about 2139.3358332838.

Subtracting from 9791221978 its reverse (8791221979), we obtain a palindrome (999999999).

The spelling of 9791221978 in words is "nine billion, seven hundred ninety-one million, two hundred twenty-one thousand, nine hundred seventy-eight".