21542809863 has 4 divisors (see below), whose sum is σ = 28723746488. Its totient is φ = 14361873240.

The previous prime is 21542809859. The next prime is 21542809909. The reversal of 21542809863 is 36890824512.

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

It is not a de Polignac number, because 21542809863 - 2² = 21542809859 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542809163) 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, 3590468308 + ... + 3590468313.

It is an arithmetic number, because the mean of its divisors is an integer number (7180936622).

Almost surely, 2^21542809863 is an apocalyptic number.

21542809863 is a deficient number, since it is larger than the sum of its proper divisors (7180936625).

21542809863 is an equidigital number, since it uses as much as digits as its factorization.

21542809863 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7180936624.

The product of its (nonzero) digits is 829440, while the sum is 48.

It can be divided in two parts, 21542 and 809863, that added together give a triangular number (831405 = T₁₂₈₉).

The spelling of 21542809863 in words is "twenty-one billion, five hundred forty-two million, eight hundred nine thousand, eight hundred sixty-three".