21688424 has 32 divisors (see below), whose sum is σ = 43276800. Its totient is φ = 10160640.

The previous prime is 21688421. The next prime is 21688427. The reversal of 21688424 is 42488612.

It is an interprime number because it is at equal distance from previous prime (21688421) and next prime (21688427).

It is not an unprimeable number, because it can be changed into a prime (21688421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14009 + ... + 15479.

It is an arithmetic number, because the mean of its divisors is an integer number (1352400).

Almost surely, 2^21688424 is an apocalyptic number.

It is an amenable number.

21688424 is a deficient number, since it is larger than the sum of its proper divisors (21588376).

21688424 is a wasteful number, since it uses less digits than its factorization.

21688424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1593 (or 1589 counting only the distinct ones).

The product of its digits is 24576, while the sum is 35.

The square root of 21688424 is about 4657.0832073305. The cubic root of 21688424 is about 278.8748384099.

The spelling of 21688424 in words is "twenty-one million, six hundred eighty-eight thousand, four hundred twenty-four".