21408887 has 4 divisors (see below), whose sum is σ = 21477600. Its totient is φ = 21340176.

The previous prime is 21408851. The next prime is 21408901. The reversal of 21408887 is 78880412.

It is a happy number.

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 21408887 - 2⁶ = 21408823 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 21408887.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21408787) 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, 33887 + ... + 34512.

It is an arithmetic number, because the mean of its divisors is an integer number (5369400).

Almost surely, 2^21408887 is an apocalyptic number.

21408887 is a deficient number, since it is larger than the sum of its proper divisors (68713).

21408887 is an equidigital number, since it uses as much as digits as its factorization.

21408887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68712.

The product of its (nonzero) digits is 28672, while the sum is 38.

The square root of 21408887 is about 4626.9738490724. The cubic root of 21408887 is about 277.6715363963.

The spelling of 21408887 in words is "twenty-one million, four hundred eight thousand, eight hundred eighty-seven".