21543361221 has 8 divisors (see below), whose sum is σ = 28896485184. Its totient is φ = 14276239040.

The previous prime is 21543361219. The next prime is 21543361237. The reversal of 21543361221 is 12216334512.

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 21543361221 - 2¹ = 21543361219 is a prime.

It is a super-4 number, since 4×21543361221⁴ (a number of 42 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21543361291) 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, 21499860 + ... + 21500861.

It is an arithmetic number, because the mean of its divisors is an integer number (3612060648).

Almost surely, 2^21543361221 is an apocalyptic number.

It is an amenable number.

21543361221 is a deficient number, since it is larger than the sum of its proper divisors (7353123963).

21543361221 is a wasteful number, since it uses less digits than its factorization.

21543361221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43000891.

The product of its digits is 8640, while the sum is 30.

Adding to 21543361221 its reverse (12216334512), we get a palindrome (33759695733).

The spelling of 21543361221 in words is "twenty-one billion, five hundred forty-three million, three hundred sixty-one thousand, two hundred twenty-one".