21000221221 has 16 divisors (see below), whose sum is σ = 24863964160. Its totient is φ = 17356602240.

The previous prime is 21000221189. The next prime is 21000221243. The reversal of 21000221221 is 12212200012.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21000221221 - 2⁵ = 21000221189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000221521) 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, 114576 + ... + 234793.

It is an arithmetic number, because the mean of its divisors is an integer number (1553997760).

Almost surely, 2^21000221221 is an apocalyptic number.

It is an amenable number.

21000221221 is a deficient number, since it is larger than the sum of its proper divisors (3863742939).

21000221221 is a wasteful number, since it uses less digits than its factorization.

21000221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 349684.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21000221221 its reverse (12212200012), we get a palindrome (33212421233).

The spelling of 21000221221 in words is "twenty-one billion, two hundred twenty-one thousand, two hundred twenty-one".