21542111221 has 8 divisors (see below), whose sum is σ = 22988897280. Its totient is φ = 20115281088.

The previous prime is 21542111197. The next prime is 21542111249. The reversal of 21542111221 is 12211124512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21542111221 - 2⁵ = 21542111189 is a prime.

It is a super-2 number, since 2×21542111221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21542111192 and 21542111201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542111281) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4986751 + ... + 4991068.

It is an arithmetic number, because the mean of its divisors is an integer number (2873612160).

Almost surely, 2^21542111221 is an apocalyptic number.

It is an amenable number.

21542111221 is a deficient number, since it is larger than the sum of its proper divisors (1446786059).

21542111221 is a wasteful number, since it uses less digits than its factorization.

21542111221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9977963.

The product of its digits is 320, while the sum is 22.

Adding to 21542111221 its reverse (12211124512), we get a palindrome (33753235733).

The spelling of 21542111221 in words is "twenty-one billion, five hundred forty-two million, one hundred eleven thousand, two hundred twenty-one".