21221012221 has 4 divisors (see below), whose sum is σ = 21621408732. Its totient is φ = 20820615712.

The previous prime is 21221012213. The next prime is 21221012251. The reversal of 21221012221 is 12221012212.

It is a happy number.

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 5567248996 + 15653763225 = 74614^2 + 125115^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221012221 - 2³ = 21221012213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21221012195 and 21221012204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221012251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 200198176 + ... + 200198281.

It is an arithmetic number, because the mean of its divisors is an integer number (5405352183).

Almost surely, 2^21221012221 is an apocalyptic number.

It is an amenable number.

21221012221 is a deficient number, since it is larger than the sum of its proper divisors (400396511).

21221012221 is an equidigital number, since it uses as much as digits as its factorization.

21221012221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400396510.

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

Adding to 21221012221 its reverse (12221012212), we get a palindrome (33442024433).

Subtracting from 21221012221 its reverse (12221012212), we obtain a palindrome (9000000009).

The spelling of 21221012221 in words is "twenty-one billion, two hundred twenty-one million, twelve thousand, two hundred twenty-one".