21536 has 12 divisors (see below), whose sum is σ = 42462. Its totient is φ = 10752.

The previous prime is 21529. The next prime is 21557. The reversal of 21536 is 63512.

It can be written as a sum of positive squares in only one way, i.e., 19600 + 1936 = 140^2 + 44^2 .

It is a nialpdrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 305 + ... + 368.

2²¹⁵³⁶ is an apocalyptic number.

It is an amenable number.

21536 is a deficient number, since it is larger than the sum of its proper divisors (20926).

21536 is an equidigital number, since it uses as much as digits as its factorization.

21536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 683 (or 675 counting only the distinct ones).

The product of its digits is 180, while the sum is 17.

The square root of 21536 is about 146.7514906228. The cubic root of 21536 is about 27.8220000791.

The spelling of 21536 in words is "twenty-one thousand, five hundred thirty-six".