21021111123 has 4 divisors (see below), whose sum is σ = 28028148168. Its totient is φ = 14014074080.

The previous prime is 21021111049. The next prime is 21021111131. The reversal of 21021111123 is 32111112012.

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 21021111123 - 2¹² = 21021107027 is a prime.

It is a super-2 number, since 2×21021111123² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21021111173) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3503518518 + ... + 3503518523.

It is an arithmetic number, because the mean of its divisors is an integer number (7007037042).

Almost surely, 2^21021111123 is an apocalyptic number.

21021111123 is a deficient number, since it is larger than the sum of its proper divisors (7007037045).

21021111123 is an equidigital number, since it uses as much as digits as its factorization.

21021111123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7007037044.

The product of its (nonzero) digits is 24, while the sum is 15.

Adding to 21021111123 its reverse (32111112012), we get a palindrome (53132223135).

The spelling of 21021111123 in words is "twenty-one billion, twenty-one million, one hundred eleven thousand, one hundred twenty-three".