21002120221 has 4 divisors (see below), whose sum is σ = 21289820572.
Its totient is φ = 20714419872.
The previous prime is 21002120213. The next prime is 21002120257. The reversal of 21002120221 is 12202120012.
Adding to 21002120221 its reverse (12202120012), we get a palindrome (33204240233).
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 14226525625 + 6775594596 = 119275^2 + 82314^2
It is a cyclic number.
It is not a de Polignac number, because 21002120221 - 23 = 21002120213 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 (21002120261) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (19) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143850066 + ... + 143850211.
It is an arithmetic number, because the mean of its divisors is an integer number (5322455143).
Almost surely, 221002120221 is an apocalyptic number.
It is an amenable number.
21002120221 is a deficient number, since it is larger than the sum of its proper divisors (287700351).
21002120221 is an equidigital number, since it uses as much as digits as its factorization.
21002120221 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 287700350.
The product of its (nonzero) digits is 32, while the sum is 13.
The spelling of 21002120221 in words is "twenty-one billion, two million, one hundred twenty thousand, two hundred twenty-one".