21201121212221 has 16 divisors (see below), whose sum is σ = 21942601758000. Its totient is φ = 20460336960000.

The previous prime is 21201121212217. The next prime is 21201121212223. The reversal of 21201121212221 is 12221212110212.

It can be written as a sum of positive squares in 8 ways, for example, as 7205632996 + 21193915579225 = 84886^2 + 4603685^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201121212221 - 2² = 21201121212217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21201121212193 and 21201121212202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201121212223) 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, 611865305 + ... + 611899953.

It is an arithmetic number, because the mean of its divisors is an integer number (1371412609875).

Almost surely, 2^{21201121212221} is an apocalyptic number.

It is an amenable number.

21201121212221 is a deficient number, since it is larger than the sum of its proper divisors (741480545779).

21201121212221 is a wasteful number, since it uses less digits than its factorization.

21201121212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44080.

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

Adding to 21201121212221 its reverse (12221212110212), we get a palindrome (33422333322433).

It can be divided in two parts, 2120112 and 1212221, that added together give a palindrome (3332333).

The spelling of 21201121212221 in words is "twenty-one trillion, two hundred one billion, one hundred twenty-one million, two hundred twelve thousand, two hundred twenty-one".