21111212101211 has 4 divisors (see below), whose sum is σ = 21229151833800. Its totient is φ = 20993272368624.

The previous prime is 21111212101193. The next prime is 21111212101249. The reversal of 21111212101211 is 11210121211112.

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 21111212101211 - 2³⁴ = 21094032232027 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 21111212101211.

It is not an unprimeable number, because it can be changed into a prime (21111212101271) 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, 58969866026 + ... + 58969866383.

It is an arithmetic number, because the mean of its divisors is an integer number (5307287958450).

Almost surely, 2^{21111212101211} is an apocalyptic number.

21111212101211 is a deficient number, since it is larger than the sum of its proper divisors (117939732589).

21111212101211 is a wasteful number, since it uses less digits than its factorization.

21111212101211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117939732588.

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

Adding to 21111212101211 its reverse (11210121211112), we get a palindrome (32321333312323).

The spelling of 21111212101211 in words is "twenty-one trillion, one hundred eleven billion, two hundred twelve million, one hundred one thousand, two hundred eleven".