21847543491 has 4 divisors (see below), whose sum is σ = 29130057992. Its totient is φ = 14565028992.

The previous prime is 21847543463. The next prime is 21847543493. The reversal of 21847543491 is 19434574812.

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

It is not a de Polignac number, because 21847543491 - 2⁷ = 21847543363 is a prime.

It is a super-2 number, since 2×21847543491² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21847543491.

It is not an unprimeable number, because it can be changed into a prime (21847543493) 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 3 ways as a sum of consecutive naturals, for example, 3641257246 + ... + 3641257251.

It is an arithmetic number, because the mean of its divisors is an integer number (7282514498).

Almost surely, 2^21847543491 is an apocalyptic number.

21847543491 is a deficient number, since it is larger than the sum of its proper divisors (7282514501).

21847543491 is an equidigital number, since it uses as much as digits as its factorization.

21847543491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7282514500.

The product of its digits is 967680, while the sum is 48.

The spelling of 21847543491 in words is "twenty-one billion, eight hundred forty-seven million, five hundred forty-three thousand, four hundred ninety-one".