21001222131221 has 4 divisors (see below), whose sum is σ = 21001232966112. Its totient is φ = 21001211296332.

The previous prime is 21001222131157. The next prime is 21001222131293. The reversal of 21001222131221 is 12213122210012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21001222131221 - 2⁶ = 21001222131157 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001222131193 and 21001222131202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001222131521) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1625081 + ... + 6681566.

It is an arithmetic number, because the mean of its divisors is an integer number (5250308241528).

Almost surely, 2^{21001222131221} is an apocalyptic number.

It is an amenable number.

21001222131221 is a deficient number, since it is larger than the sum of its proper divisors (10834891).

21001222131221 is an equidigital number, since it uses as much as digits as its factorization.

21001222131221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10834890.

The product of its (nonzero) digits is 192, while the sum is 20.

Adding to 21001222131221 its reverse (12213122210012), we get a palindrome (33214344341233).

The spelling of 21001222131221 in words is "twenty-one trillion, one billion, two hundred twenty-two million, one hundred thirty-one thousand, two hundred twenty-one".