21202221 has 16 divisors (see below), whose sum is σ = 29187648. Its totient is φ = 13680000.

The previous prime is 21202211. The next prime is 21202261. The reversal of 21202221 is 12220212.

It is not a de Polignac number, because 21202221 - 2⁵ = 21202189 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21202197 and 21202206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21202201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27481 + ... + 28241.

It is an arithmetic number, because the mean of its divisors is an integer number (1824228).

Almost surely, 2^21202221 is an apocalyptic number.

It is an amenable number.

21202221 is a deficient number, since it is larger than the sum of its proper divisors (7985427).

21202221 is a wasteful number, since it uses less digits than its factorization.

21202221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1052.

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 21202221 is about 4604.5869521598. The cubic root of 21202221 is about 276.7751654256.

Adding to 21202221 its reverse (12220212), we get a palindrome (33422433).

Subtracting from 21202221 its reverse (12220212), we obtain a square (8982009 = 2997²).

The spelling of 21202221 in words is "twenty-one million, two hundred two thousand, two hundred twenty-one".