21688867 has 4 divisors (see below), whose sum is σ = 21994416. Its totient is φ = 21383320.

The previous prime is 21688817. The next prime is 21688873. The reversal of 21688867 is 76888612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21688867 - 2¹⁵ = 21656099 is a prime.

It is a Duffinian 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 3 ways as a sum of consecutive naturals, for example, 152668 + ... + 152809.

It is an arithmetic number, because the mean of its divisors is an integer number (5498604).

Almost surely, 2^21688867 is an apocalyptic number.

21688867 is a deficient number, since it is larger than the sum of its proper divisors (305549).

21688867 is an equidigital number, since it uses as much as digits as its factorization.

21688867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 305548.

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

The square root of 21688867 is about 4657.1307690465. The cubic root of 21688867 is about 278.8767371296.

The spelling of 21688867 in words is "twenty-one million, six hundred eighty-eight thousand, eight hundred sixty-seven".