21011020221221 has 4 divisors (see below), whose sum is σ = 21018851390592. Its totient is φ = 21003189051852.

The previous prime is 21011020221209. The next prime is 21011020221223. The reversal of 21011020221221 is 12212202011012.

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 not a de Polignac number, because 21011020221221 - 2³⁰ = 21009946479397 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 21011020221221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011020221223) 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, 3915580661 + ... + 3915586026.

It is an arithmetic number, because the mean of its divisors is an integer number (5254712847648).

Almost surely, 2^{21011020221221} is an apocalyptic number.

It is an amenable number.

21011020221221 is a deficient number, since it is larger than the sum of its proper divisors (7831169371).

21011020221221 is an equidigital number, since it uses as much as digits as its factorization.

21011020221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7831169370.

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

Adding to 21011020221221 its reverse (12212202011012), we get a palindrome (33223222232233).

The spelling of 21011020221221 in words is "twenty-one trillion, eleven billion, twenty million, two hundred twenty-one thousand, two hundred twenty-one".