21033111221 has 2 divisors, whose sum is σ = 21033111222. Its totient is φ = 21033111220.

The previous prime is 21033111157. The next prime is 21033111227. The reversal of 21033111221 is 12211133012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20789314225 + 243796996 = 144185^2 + 15614^2 .

It is a cyclic number.

It is not a de Polignac number, because 21033111221 - 2⁶ = 21033111157 is a prime.

It is a super-2 number, since 2×21033111221² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21033111221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21033111227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10516555610 + 10516555611.

It is an arithmetic number, because the mean of its divisors is an integer number (10516555611).

Almost surely, 2^21033111221 is an apocalyptic number.

It is an amenable number.

21033111221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21033111221 is an equidigital number, since it uses as much as digits as its factorization.

21033111221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 17.

Adding to 21033111221 its reverse (12211133012), we get a palindrome (33244244233).

The spelling of 21033111221 in words is "twenty-one billion, thirty-three million, one hundred eleven thousand, two hundred twenty-one".