21104 has 10 divisors (see below), whose sum is σ = 40920. Its totient is φ = 10544.

The previous prime is 21101. The next prime is 21107. The reversal of 21104 is 40112.

It is an interprime number because it is at equal distance from previous prime (21101) and next prime (21107).

It is a Harshad number since it is a multiple of its sum of digits (8).

It is a junction number, because it is equal to n+sod(n) for n = 21091 and 21100.

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 as a sum of consecutive naturals, namely, 644 + ... + 675.

It is an arithmetic number, because the mean of its divisors is an integer number (4092).

2²¹¹⁰⁴ is an apocalyptic number.

It is an amenable number.

21104 is a deficient number, since it is larger than the sum of its proper divisors (19816).

21104 is a wasteful number, since it uses less digits than its factorization.

21104 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1327 (or 1321 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 21104 is about 145.2721583787. The cubic root of 21104 is about 27.6347109311.

Adding to 21104 its reverse (40112), we get a palindrome (61216).

It can be divided in two parts, 21 and 104, that added together give a cube (125 = 5³).

The spelling of 21104 in words is "twenty-one thousand, one hundred four", and thus it is an iban number.