21304 has 8 divisors (see below), whose sum is σ = 39960. Its totient is φ = 10648.

The previous prime is 21283. The next prime is 21313. The reversal of 21304 is 40312.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1324 + ... + 1339.

It is an arithmetic number, because the mean of its divisors is an integer number (4995).

2²¹³⁰⁴ is an apocalyptic number.

It is an amenable number.

21304 is a deficient number, since it is larger than the sum of its proper divisors (18656).

21304 is a wasteful number, since it uses less digits than its factorization.

21304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2669 (or 2665 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 10.

The square root of 21304 is about 145.9588983242. The cubic root of 21304 is about 27.7217335200.

Adding to 21304 its reverse (40312), we get a palindrome (61616).

It can be divided in two parts, 21 and 304, that added together give a triangular number (325 = T₂₅).

The spelling of 21304 in words is "twenty-one thousand, three hundred four", and thus it is an iban number.