21000001220221 has 4 divisors (see below), whose sum is σ = 21003153906844. Its totient is φ = 20996848533600.

The previous prime is 21000001220203. The next prime is 21000001220249. The reversal of 21000001220221 is 12202210000012.

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 10745211884121 + 10254789336100 = 3277989^2 + 3202310^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000001220221 - 2¹⁵ = 21000001187453 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000001220251) 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, 1576333320 + ... + 1576346641.

It is an arithmetic number, because the mean of its divisors is an integer number (5250788476711).

Almost surely, 2^{21000001220221} is an apocalyptic number.

It is an amenable number.

21000001220221 is a deficient number, since it is larger than the sum of its proper divisors (3152686623).

21000001220221 is an equidigital number, since it uses as much as digits as its factorization.

21000001220221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3152686622.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21000001220221 its reverse (12202210000012), we get a palindrome (33202211220233).

The spelling of 21000001220221 in words is "twenty-one trillion, one million, two hundred twenty thousand, two hundred twenty-one".