21244021221 has 4 divisors (see below), whose sum is σ = 28325361632. Its totient is φ = 14162680812.

The previous prime is 21244021213. The next prime is 21244021237. The reversal of 21244021221 is 12212044212.

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 not a de Polignac number, because 21244021221 - 2³ = 21244021213 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 (21244021621) 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, 3540670201 + ... + 3540670206.

It is an arithmetic number, because the mean of its divisors is an integer number (7081340408).

Almost surely, 2^21244021221 is an apocalyptic number.

It is an amenable number.

21244021221 is a deficient number, since it is larger than the sum of its proper divisors (7081340411).

21244021221 is an equidigital number, since it uses as much as digits as its factorization.

21244021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7081340410.

The product of its (nonzero) digits is 512, while the sum is 21.

Adding to 21244021221 its reverse (12212044212), we get a palindrome (33456065433).

The spelling of 21244021221 in words is "twenty-one billion, two hundred forty-four million, twenty-one thousand, two hundred twenty-one".