21011111221 has 8 divisors (see below), whose sum is σ = 22141362080. Its totient is φ = 19883300688.

The previous prime is 21011111203. The next prime is 21011111237. The reversal of 21011111221 is 12211111012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011111221 is a prime.

It is a super-2 number, since 2×21011111221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011111201) 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 7 ways as a sum of consecutive naturals, for example, 592386 + ... + 626851.

It is an arithmetic number, because the mean of its divisors is an integer number (2767670260).

Almost surely, 2^21011111221 is an apocalyptic number.

It is an amenable number.

21011111221 is a deficient number, since it is larger than the sum of its proper divisors (1130250859).

21011111221 is a wasteful number, since it uses less digits than its factorization.

21011111221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1220163.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21011111221 its reverse (12211111012), we get a palindrome (33222222233).

The spelling of 21011111221 in words is "twenty-one billion, eleven million, one hundred eleven thousand, two hundred twenty-one".