21220111100021 has 4 divisors (see below), whose sum is σ = 22468352929452. Its totient is φ = 19971869270592.

The previous prime is 21220111100009. The next prime is 21220111100039. The reversal of 21220111100021 is 12000111102212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14656723128100 + 6563387971921 = 3828410^2 + 2561911^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220111100021 - 2¹⁴ = 21220111083637 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21220111099969 and 21220111100005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220111100081) 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, 624120914690 + ... + 624120914723.

It is an arithmetic number, because the mean of its divisors is an integer number (5617088232363).

Almost surely, 2^{21220111100021} is an apocalyptic number.

It is an amenable number.

21220111100021 is a deficient number, since it is larger than the sum of its proper divisors (1248241829431).

21220111100021 is a wasteful number, since it uses less digits than its factorization.

21220111100021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1248241829430.

The product of its (nonzero) digits is 16, while the sum is 14.

Adding to 21220111100021 its reverse (12000111102212), we get a palindrome (33220222202233).

The spelling of 21220111100021 in words is "twenty-one trillion, two hundred twenty billion, one hundred eleven million, one hundred thousand, twenty-one".