21748978491 has 8 divisors (see below), whose sum is σ = 29474025744. Its totient is φ = 14261625120.

The previous prime is 21748978487. The next prime is 21748978507. The reversal of 21748978491 is 19487984712.

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

It is not a de Polignac number, because 21748978491 - 2² = 21748978487 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 (21748978091) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 59423256 + ... + 59423621.

It is an arithmetic number, because the mean of its divisors is an integer number (3684253218).

Almost surely, 2^21748978491 is an apocalyptic number.

21748978491 is a deficient number, since it is larger than the sum of its proper divisors (7725047253).

21748978491 is a wasteful number, since it uses less digits than its factorization.

21748978491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118846941.

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

The spelling of 21748978491 in words is "twenty-one billion, seven hundred forty-eight million, nine hundred seventy-eight thousand, four hundred ninety-one".