21011221111211 has 4 divisors (see below), whose sum is σ = 21013439131992. Its totient is φ = 21009003090432.

The previous prime is 21011221111201. The next prime is 21011221111213. The reversal of 21011221111211 is 11211112211012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21011221111211 - 2³⁸ = 20736343204267 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21011221111211.

It is not an unprimeable number, because it can be changed into a prime (21011221111213) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1108996181 + ... + 1109015126.

It is an arithmetic number, because the mean of its divisors is an integer number (5253359782998).

Almost surely, 2^{21011221111211} is an apocalyptic number.

21011221111211 is a deficient number, since it is larger than the sum of its proper divisors (2218020781).

21011221111211 is an equidigital number, since it uses as much as digits as its factorization.

21011221111211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2218020780.

The product of its (nonzero) digits is 16, while the sum is 17.

Adding to 21011221111211 its reverse (11211112211012), we get a palindrome (32222333322223).

The spelling of 21011221111211 in words is "twenty-one trillion, eleven billion, two hundred twenty-one million, one hundred eleven thousand, two hundred eleven".