21135688 has 32 divisors (see below), whose sum is σ = 46065600. Its totient is φ = 8903232.

The previous prime is 21135683. The next prime is 21135691. The reversal of 21135688 is 88653112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135683) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 106 + ... + 6502.

It is an arithmetic number, because the mean of its divisors is an integer number (1439550).

Almost surely, 2^21135688 is an apocalyptic number.

21135688 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21135688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23032800).

21135688 is an abundant number, since it is smaller than the sum of its proper divisors (24929912).

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

21135688 is a wasteful number, since it uses less digits than its factorization.

21135688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6469 (or 6465 counting only the distinct ones).

The product of its digits is 11520, while the sum is 34.

The square root of 21135688 is about 4597.3566318048. The cubic root of 21135688 is about 276.4853533722.

It can be divided in two parts, 2113568 and 8, that multiplied together give a square (16908544 = 4112²).

The spelling of 21135688 in words is "twenty-one million, one hundred thirty-five thousand, six hundred eighty-eight".