21688768 has 28 divisors (see below), whose sum is σ = 43434000. Its totient is φ = 10744832.

The previous prime is 21688759. The next prime is 21688783. The reversal of 21688768 is 86788612.

It is a Smith number, since the sum of its digits (46) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 5733 + ... + 8731.

Almost surely, 2^21688768 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21688768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21717000).

21688768 is an abundant number, since it is smaller than the sum of its proper divisors (21745232).

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

21688768 is a wasteful number, since it uses less digits than its factorization.

21688768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3124 (or 3114 counting only the distinct ones).

The product of its digits is 258048, while the sum is 46.

The square root of 21688768 is about 4657.1201401725. The cubic root of 21688768 is about 278.8763128130.

The spelling of 21688768 in words is "twenty-one million, six hundred eighty-eight thousand, seven hundred sixty-eight".