21111 has 8 divisors (see below), whose sum is σ = 29184. Its totient is φ = 13560.

The previous prime is 21107. The next prime is 21121. The reversal of 21111 is 11112.

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

It is not a de Polignac number, because 21111 - 2² = 21107 is a prime.

21111 is a modest number, since divided by 111 gives 21 as remainder.

21111 is a lucky number.

It is a plaindrome in base 14.

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 21111.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21 + ... + 206.

It is an arithmetic number, because the mean of its divisors is an integer number (3648).

2²¹¹¹¹ is an apocalyptic number.

21111 is a deficient number, since it is larger than the sum of its proper divisors (8073).

21111 is a wasteful number, since it uses less digits than its factorization.

21111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261.

The product of its digits is 2, while the sum is 6.

The square root of 21111 is about 145.2962490913. The cubic root of 21111 is about 27.6377659854.

Adding to 21111 its reverse (11112), we get a palindrome (32223).

Subtracting from 21111 its reverse (11112), we obtain a palindrome (9999).

Multiplying 21111 by its reverse (11112), we get a palindrome (234585432).

It can be divided in two parts, 2111 and 1, that added together give a palindrome (2112).

The spelling of 21111 in words is "twenty-one thousand, one hundred eleven", and thus it is an iban number.