21002105221 has 4 divisors (see below), whose sum is σ = 22107479200. Its totient is φ = 19896731244.

The previous prime is 21002105213. The next prime is 21002105231. The reversal of 21002105221 is 12250120012.

It is a happy number.

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 21002105221 - 2³ = 21002105213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002105195 and 21002105204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002105231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 552686961 + ... + 552686998.

It is an arithmetic number, because the mean of its divisors is an integer number (5526869800).

Almost surely, 2^21002105221 is an apocalyptic number.

It is an amenable number.

21002105221 is a deficient number, since it is larger than the sum of its proper divisors (1105373979).

21002105221 is a wasteful number, since it uses less digits than its factorization.

21002105221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1105373978.

The product of its (nonzero) digits is 80, while the sum is 16.

Adding to 21002105221 its reverse (12250120012), we get a palindrome (33252225233).

The spelling of 21002105221 in words is "twenty-one billion, two million, one hundred five thousand, two hundred twenty-one".