21001211220221 has 8 divisors (see below), whose sum is σ = 21726672178080. Its totient is φ = 20275835679792.

The previous prime is 21001211220203. The next prime is 21001211220257. The reversal of 21001211220221 is 12202211210012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21001211220221 - 2³⁸ = 20726333313277 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 21001211220221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001211220281) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20853935 + ... + 21837788.

It is an arithmetic number, because the mean of its divisors is an integer number (2715834022260).

Almost surely, 2^{21001211220221} is an apocalyptic number.

It is an amenable number.

21001211220221 is a deficient number, since it is larger than the sum of its proper divisors (725460957859).

21001211220221 is a wasteful number, since it uses less digits than its factorization.

21001211220221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42708715.

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 21001211220221 its reverse (12202211210012), we get a palindrome (33203422430233).

The spelling of 21001211220221 in words is "twenty-one trillion, one billion, two hundred eleven million, two hundred twenty thousand, two hundred twenty-one".