21542104643 has 4 divisors (see below), whose sum is σ = 21551154528. Its totient is φ = 21533054760.

The previous prime is 21542104621. The next prime is 21542104669. The reversal of 21542104643 is 34640124512.

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

It is a cyclic number.

It is not a de Polignac number, because 21542104643 - 2¹⁰ = 21542103619 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21542106643) 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, 4521371 + ... + 4526132.

It is an arithmetic number, because the mean of its divisors is an integer number (5387788632).

Almost surely, 2^21542104643 is an apocalyptic number.

21542104643 is a deficient number, since it is larger than the sum of its proper divisors (9049885).

21542104643 is an equidigital number, since it uses as much as digits as its factorization.

21542104643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9049884.

The product of its (nonzero) digits is 23040, while the sum is 32.

The spelling of 21542104643 in words is "twenty-one billion, five hundred forty-two million, one hundred four thousand, six hundred forty-three".