21688807 has 8 divisors (see below), whose sum is σ = 24826016. Its totient is φ = 18561312.

The previous prime is 21688783. The next prime is 21688817. The reversal of 21688807 is 70888612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21688807 - 2¹⁵ = 21656039 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21688807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21688817) 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, 3253 + ... + 7345.

It is an arithmetic number, because the mean of its divisors is an integer number (3103252).

Almost surely, 2^21688807 is an apocalyptic number.

21688807 is a deficient number, since it is larger than the sum of its proper divisors (3137209).

21688807 is an equidigital number, since it uses as much as digits as its factorization.

21688807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4857.

The product of its (nonzero) digits is 43008, while the sum is 40.

The square root of 21688807 is about 4657.1243273076. The cubic root of 21688807 is about 278.8764799682.

The spelling of 21688807 in words is "twenty-one million, six hundred eighty-eight thousand, eight hundred seven".