21621306221 has 16 divisors (see below), whose sum is σ = 22962344448. Its totient is φ = 20329056000.

The previous prime is 21621306181. The next prime is 21621306233. The reversal of 21621306221 is 12260312612.

It is a happy number.

It is not a de Polignac number, because 21621306221 - 2¹⁰ = 21621305197 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 (21621306241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 80321 + ... + 222921.

It is an arithmetic number, because the mean of its divisors is an integer number (1435146528).

Almost surely, 2^21621306221 is an apocalyptic number.

It is an amenable number.

21621306221 is a deficient number, since it is larger than the sum of its proper divisors (1341038227).

21621306221 is a wasteful number, since it uses less digits than its factorization.

21621306221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142772.

The product of its (nonzero) digits is 1728, while the sum is 26.

Adding to 21621306221 its reverse (12260312612), we get a palindrome (33881618833).

The spelling of 21621306221 in words is "twenty-one billion, six hundred twenty-one million, three hundred six thousand, two hundred twenty-one".