21978478491 has 8 divisors (see below), whose sum is σ = 30019385424. Its totient is φ = 14294945280.

The previous prime is 21978478481. The next prime is 21978478493. The reversal of 21978478491 is 19487487912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21978478491 - 2⁶ = 21978478427 is a prime.

It is a Smith number, since the sum of its digits (60) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21978478493) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 89343286 + ... + 89343531.

It is an arithmetic number, because the mean of its divisors is an integer number (3752423178).

Almost surely, 2^21978478491 is an apocalyptic number.

21978478491 is a deficient number, since it is larger than the sum of its proper divisors (8040906933).

21978478491 is a wasteful number, since it uses less digits than its factorization.

21978478491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178686861.

The product of its digits is 8128512, while the sum is 60.

The spelling of 21978478491 in words is "twenty-one billion, nine hundred seventy-eight million, four hundred seventy-eight thousand, four hundred ninety-one".