21211220221121 has 12 divisors (see below), whose sum is σ = 24674484266388. Its totient is φ = 18180892874592.

The previous prime is 21211220221117. The next prime is 21211220221181. The reversal of 21211220221121 is 12112202211212.

It can be written as a sum of positive squares in 2 ways, for example, as 11053390712896 + 10157829508225 = 3324664^2 + 3187135^2 .

It is not a de Polignac number, because 21211220221121 - 2² = 21211220221117 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21211220221093 and 21211220221102.

It is not an unprimeable number, because it can be changed into a prime (21211220221111) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4264595 + ... + 7785191.

It is an arithmetic number, because the mean of its divisors is an integer number (2056207022199).

Almost surely, 2^{21211220221121} is an apocalyptic number.

It is an amenable number.

21211220221121 is a deficient number, since it is larger than the sum of its proper divisors (3463264045267).

21211220221121 is a wasteful number, since it uses less digits than its factorization.

21211220221121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3643568 (or 3643561 counting only the distinct ones).

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

Adding to 21211220221121 its reverse (12112202211212), we get a palindrome (33323422432333).

It can be divided in two parts, 2 and 1211220221121, that multiplied together give a palindrome (2422440442242).

The spelling of 21211220221121 in words is "twenty-one trillion, two hundred eleven billion, two hundred twenty million, two hundred twenty-one thousand, one hundred twenty-one".