21108887 has 4 divisors (see below), whose sum is σ = 21162456. Its totient is φ = 21055320.

The previous prime is 21108881. The next prime is 21108889. The reversal of 21108887 is 78880112.

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 21108887 - 2⁸ = 21108631 is a prime.

It is a super-2 number, since 2×21108887² = 891170220757538, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21108881) 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, 26189 + ... + 26982.

It is an arithmetic number, because the mean of its divisors is an integer number (5290614).

Almost surely, 2^21108887 is an apocalyptic number.

21108887 is a deficient number, since it is larger than the sum of its proper divisors (53569).

21108887 is an equidigital number, since it uses as much as digits as its factorization.

21108887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53568.

The product of its (nonzero) digits is 7168, while the sum is 35.

The square root of 21108887 is about 4594.4408800201. The cubic root of 21108887 is about 276.3684386658.

Adding to 21108887 its reverse (78880112), we get a palindrome (99988999).

The spelling of 21108887 in words is "twenty-one million, one hundred eight thousand, eight hundred eighty-seven".