21535638 has 16 divisors (see below), whose sum is σ = 44461056. Its totient is φ = 6946920.

The previous prime is 21535621. The next prime is 21535639. The reversal of 21535638 is 83653512.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21535599 and 21535608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21535639) 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, 57706 + ... + 58077.

It is an arithmetic number, because the mean of its divisors is an integer number (2778816).

Almost surely, 2^21535638 is an apocalyptic number.

21535638 is an abundant number, since it is smaller than the sum of its proper divisors (22925418).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21535638 is a wasteful number, since it uses less digits than its factorization.

21535638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115819.

The product of its digits is 21600, while the sum is 33.

The square root of 21535638 is about 4640.6506009395. The cubic root of 21535638 is about 278.2184419100.

It can be divided in two parts, 215 and 35638, that added together give a palindrome (35853).

The spelling of 21535638 in words is "twenty-one million, five hundred thirty-five thousand, six hundred thirty-eight".