21307 has 8 divisors (see below), whose sum is σ = 25200. Its totient is φ = 17760.

The previous prime is 21283. The next prime is 21313. The reversal of 21307 is 70312.

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

It is a cyclic number.

It is not a de Polignac number, because 21307 - 2⁷ = 21179 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a Duffinian number.

21307 is a lucky number.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21317) 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, 69 + ... + 217.

It is an arithmetic number, because the mean of its divisors is an integer number (3150).

2²¹³⁰⁷ is an apocalyptic number.

21307 is a deficient number, since it is larger than the sum of its proper divisors (3893).

21307 is a wasteful number, since it uses less digits than its factorization.

21307 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173.

The product of its (nonzero) digits is 42, while the sum is 13.

The square root of 21307 is about 145.9691748281. The cubic root of 21307 is about 27.7230347044.

Adding to 21307 its reverse (70312), we get a palindrome (91619).

The spelling of 21307 in words is "twenty-one thousand, three hundred seven", and thus it is an iban number.