21100220021221 has 16 divisors (see below), whose sum is σ = 24374227200768. Its totient is φ = 18052345267200.

The previous prime is 21100220021173. The next prime is 21100220021291. The reversal of 21100220021221 is 12212002200112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21100220021221 - 2²³ = 21100211632613 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21100220021195 and 21100220021204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100220021291) 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, 1550820 + ... + 6678733.

It is an arithmetic number, because the mean of its divisors is an integer number (1523389200048).

Almost surely, 2^{21100220021221} is an apocalyptic number.

It is an amenable number.

21100220021221 is a deficient number, since it is larger than the sum of its proper divisors (3274007179547).

21100220021221 is a wasteful number, since it uses less digits than its factorization.

21100220021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8243292.

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

Adding to 21100220021221 its reverse (12212002200112), we get a palindrome (33312222221333).

The spelling of 21100220021221 in words is "twenty-one trillion, one hundred billion, two hundred twenty million, twenty-one thousand, two hundred twenty-one".