21221201222021 has 4 divisors (see below), whose sum is σ = 21621601245132. Its totient is φ = 20820801198912.

The previous prime is 21221201222017. The next prime is 21221201222033. The reversal of 21221201222021 is 12022210212212.

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 11307172912996 + 9914028309025 = 3362614^2 + 3148655^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221201222021 - 2² = 21221201222017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21221201221984 and 21221201222002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221201222321) 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, 200200011476 + ... + 200200011581.

It is an arithmetic number, because the mean of its divisors is an integer number (5405400311283).

Almost surely, 2^{21221201222021} is an apocalyptic number.

It is an amenable number.

21221201222021 is a deficient number, since it is larger than the sum of its proper divisors (400400023111).

21221201222021 is an equidigital number, since it uses as much as digits as its factorization.

21221201222021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400400023110.

The product of its (nonzero) digits is 256, while the sum is 20.

Adding to 21221201222021 its reverse (12022210212212), we get a palindrome (33243411434233).

The spelling of 21221201222021 in words is "twenty-one trillion, two hundred twenty-one billion, two hundred one million, two hundred twenty-two thousand, twenty-one".