21221210212121 has 32 divisors (see below), whose sum is σ = 21853780508160. Its totient is φ = 20599095328000.

The previous prime is 21221210212043. The next prime is 21221210212127. The reversal of 21221210212121 is 12121201212212.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21221210212121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21221210212093 and 21221210212102.

It is not an unprimeable number, because it can be changed into a prime (21221210212127) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4523811386 + ... + 4523816076.

It is an arithmetic number, because the mean of its divisors is an integer number (682930640880).

Almost surely, 2^{21221210212121} is an apocalyptic number.

It is an amenable number.

21221210212121 is a deficient number, since it is larger than the sum of its proper divisors (632570296039).

21221210212121 is a wasteful number, since it uses less digits than its factorization.

21221210212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7045.

The product of its (nonzero) digits is 128, while the sum is 20.

Adding to 21221210212121 its reverse (12121201212212), we get a palindrome (33342411424333).

The spelling of 21221210212121 in words is "twenty-one trillion, two hundred twenty-one billion, two hundred ten million, two hundred twelve thousand, one hundred twenty-one".