21011111123 has 4 divisors (see below), whose sum is σ = 21011402040. Its totient is φ = 21010820208.

The previous prime is 21011111119. The next prime is 21011111129. The reversal of 21011111123 is 32111111012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21011111123 - 2² = 21011111119 is a prime.

It is a super-2 number, since 2×21011111123² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011111098 and 21011111107.

It is not an unprimeable number, because it can be changed into a prime (21011111129) 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 3 ways as a sum of consecutive naturals, for example, 54548 + ... + 212126.

It is an arithmetic number, because the mean of its divisors is an integer number (5252850510).

Almost surely, 2^21011111123 is an apocalyptic number.

21011111123 is a deficient number, since it is larger than the sum of its proper divisors (290917).

21011111123 is a wasteful number, since it uses less digits than its factorization.

21011111123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290916.

The product of its (nonzero) digits is 12, while the sum is 14.

Adding to 21011111123 its reverse (32111111012), we get a palindrome (53122222135).

The spelling of 21011111123 in words is "twenty-one billion, eleven million, one hundred eleven thousand, one hundred twenty-three".