21875820491 has 4 divisors (see below), whose sum is σ = 25000937712. Its totient is φ = 18750703272.

The previous prime is 21875820451. The next prime is 21875820529. The reversal of 21875820491 is 19402857812.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21875820491 - 2³⁴ = 4695951307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21875820451) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1562558600 + ... + 1562558613.

It is an arithmetic number, because the mean of its divisors is an integer number (6250234428).

Almost surely, 2^21875820491 is an apocalyptic number.

21875820491 is a deficient number, since it is larger than the sum of its proper divisors (3125117221).

21875820491 is an equidigital number, since it uses as much as digits as its factorization.

21875820491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3125117220.

The product of its (nonzero) digits is 322560, while the sum is 47.

The spelling of 21875820491 in words is "twenty-one billion, eight hundred seventy-five million, eight hundred twenty thousand, four hundred ninety-one".