21535 has 8 divisors (see below), whose sum is σ = 26640. Its totient is φ = 16704.

The previous prime is 21529. The next prime is 21557. The reversal of 21535 is 53512.

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 21535 - 2⁵ = 21503 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 259 + ... + 331.

It is an arithmetic number, because the mean of its divisors is an integer number (3330).

2²¹⁵³⁵ is an apocalyptic number.

21535 is a deficient number, since it is larger than the sum of its proper divisors (5105).

21535 is an equidigital number, since it uses as much as digits as its factorization.

21535 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137.

The product of its digits is 150, while the sum is 16.

The square root of 21535 is about 146.7480834628. The cubic root of 21535 is about 27.8215694447.

The spelling of 21535 in words is "twenty-one thousand, five hundred thirty-five".