21021220212221 has 16 divisors (see below), whose sum is σ = 21524652474624. Its totient is φ = 20521866228864.

The previous prime is 21021220212143. The next prime is 21021220212227. The reversal of 21021220212221 is 12221202212012.

It is a cyclic number.

It is not a de Polignac number, because 21021220212221 - 2¹⁸ = 21021219950077 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21021220212193 and 21021220212202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021220212227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17280800 + ... + 18457206.

It is an arithmetic number, because the mean of its divisors is an integer number (1345290779664).

Almost surely, 2^{21021220212221} is an apocalyptic number.

It is an amenable number.

21021220212221 is a deficient number, since it is larger than the sum of its proper divisors (503432262403).

21021220212221 is a wasteful number, since it uses less digits than its factorization.

21021220212221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1178140.

The product of its (nonzero) digits is 256, while the sum is 20.

Adding to 21021220212221 its reverse (12221202212012), we get a palindrome (33242422424233).

The spelling of 21021220212221 in words is "twenty-one trillion, twenty-one billion, two hundred twenty million, two hundred twelve thousand, two hundred twenty-one".