21542220541 has 4 divisors (see below), whose sum is σ = 21615743772. Its totient is φ = 21468697312.

The previous prime is 21542220529. The next prime is 21542220589. The reversal of 21542220541 is 14502224512.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 18980848441 + 2561372100 = 137771^2 + 50610^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21542220541 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 (21542220521) 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, 36761176 + ... + 36761761.

It is an arithmetic number, because the mean of its divisors is an integer number (5403935943).

Almost surely, 2^21542220541 is an apocalyptic number.

It is an amenable number.

21542220541 is a deficient number, since it is larger than the sum of its proper divisors (73523231).

21542220541 is an equidigital number, since it uses as much as digits as its factorization.

21542220541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73523230.

The product of its (nonzero) digits is 6400, while the sum is 28.

The spelling of 21542220541 in words is "twenty-one billion, five hundred forty-two million, two hundred twenty thousand, five hundred forty-one".