21020001222221 has 4 divisors (see below), whose sum is σ = 21022644922944. Its totient is φ = 21017357521500.

The previous prime is 21020001222197. The next prime is 21020001222271. The reversal of 21020001222221 is 12222210002012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020001222221 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21020001222221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020001222271) 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, 1321838435 + ... + 1321854336.

It is an arithmetic number, because the mean of its divisors is an integer number (5255661230736).

Almost surely, 2^{21020001222221} is an apocalyptic number.

It is an amenable number.

21020001222221 is a deficient number, since it is larger than the sum of its proper divisors (2643700723).

21020001222221 is an equidigital number, since it uses as much as digits as its factorization.

21020001222221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2643700722.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21020001222221 its reverse (12222210002012), we get a palindrome (33242211224233).

The spelling of 21020001222221 in words is "twenty-one trillion, twenty billion, one million, two hundred twenty-two thousand, two hundred twenty-one".