21121220221 has 8 divisors (see below), whose sum is σ = 21289292064. Its totient is φ = 20953806960.

The previous prime is 21121220177. The next prime is 21121220227. The reversal of 21121220221 is 12202212112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21121220221 - 2⁷ = 21121220093 is a prime.

It is a super-2 number, since 2×21121220221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21121220195 and 21121220204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121220227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 100150 + ... + 228631.

It is an arithmetic number, because the mean of its divisors is an integer number (2661161508).

Almost surely, 2^21121220221 is an apocalyptic number.

It is an amenable number.

21121220221 is a deficient number, since it is larger than the sum of its proper divisors (168071843).

21121220221 is a wasteful number, since it uses less digits than its factorization.

21121220221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329291.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21121220221 its reverse (12202212112), we get a palindrome (33323432333).

The spelling of 21121220221 in words is "twenty-one billion, one hundred twenty-one million, two hundred twenty thousand, two hundred twenty-one".