21111001221 has 4 divisors (see below), whose sum is σ = 28148001632. Its totient is φ = 14074000812.

The previous prime is 21111001193. The next prime is 21111001243. The reversal of 21111001221 is 12210011112.

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 not a de Polignac number, because 21111001221 - 2⁵ = 21111001189 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111001197 and 21111001206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111001291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3518500201 + ... + 3518500206.

It is an arithmetic number, because the mean of its divisors is an integer number (7037000408).

Almost surely, 2^21111001221 is an apocalyptic number.

It is an amenable number.

21111001221 is a deficient number, since it is larger than the sum of its proper divisors (7037000411).

21111001221 is an equidigital number, since it uses as much as digits as its factorization.

21111001221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7037000410.

The product of its (nonzero) digits is 8, while the sum is 12.

Adding to 21111001221 its reverse (12210011112), we get a palindrome (33321012333).

The spelling of 21111001221 in words is "twenty-one billion, one hundred eleven million, one thousand, two hundred twenty-one".