21103 has 4 divisors (see below), whose sum is σ = 21600. Its totient is φ = 20608.
The previous prime is 21101. The next prime is 21107. The reversal of 21103 is 30112.
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 21103 - 21 = 21101 is a prime.
It is a Duffinian number.
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 3 ways as a sum of consecutive naturals, for example, 178 + ... + 271.
It is an arithmetic number, because the mean of its divisors is an integer number (5400).
221103 is an apocalyptic number.
21103 is a deficient number, since it is larger than the sum of its proper divisors (497).
21103 is an equidigital number, since it uses as much as digits as its factorization.
21103 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 496.
The product of its (nonzero) digits is 6, while the sum is 7.
The square root of 21103 is about 145.2687165222. The cubic root of 21103 is about 27.6342744397.
Adding to 21103 its reverse (30112), we get a palindrome (51215).
Subtracting 21103 from its reverse (30112), we obtain a palindrome (9009).
The spelling of 21103 in words is "twenty-one thousand, one hundred three", and thus it is an iban number.
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