21202011221 has 4 divisors (see below), whose sum is σ = 21214731552. Its totient is φ = 21189290892.

The previous prime is 21202011199. The next prime is 21202011241. The reversal of 21202011221 is 12211020212.

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 a de Polignac number, because none of the positive numbers 2^k-21202011221 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21202011196 and 21202011205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21202011241) 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, 6357665 + ... + 6360998.

It is an arithmetic number, because the mean of its divisors is an integer number (5303682888).

Almost surely, 2^21202011221 is an apocalyptic number.

It is an amenable number.

21202011221 is a deficient number, since it is larger than the sum of its proper divisors (12720331).

21202011221 is a wasteful number, since it uses less digits than its factorization.

21202011221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12720330.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21202011221 its reverse (12211020212), we get a palindrome (33413031433).

The spelling of 21202011221 in words is "twenty-one billion, two hundred two million, eleven thousand, two hundred twenty-one".