21516887 has 16 divisors (see below), whose sum is σ = 25505280. Its totient is φ = 17770272.

The previous prime is 21516877. The next prime is 21516893. The reversal of 21516887 is 78861512.

It is a cyclic number.

It is not a de Polignac number, because 21516887 - 2⁴ = 21516871 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 21516887.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21516827) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 21398 + ... + 22380.

It is an arithmetic number, because the mean of its divisors is an integer number (1594080).

Almost surely, 2^21516887 is an apocalyptic number.

21516887 is a deficient number, since it is larger than the sum of its proper divisors (3988393).

21516887 is an equidigital number, since it uses as much as digits as its factorization.

21516887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1102.

The product of its digits is 26880, while the sum is 38.

The square root of 21516887 is about 4638.6298623624. The cubic root of 21516887 is about 278.1376705417.

It can be divided in two parts, 2151688 and 7, that multiplied together give a triangular number (15061816 = T₅₄₈₈).

The spelling of 21516887 in words is "twenty-one million, five hundred sixteen thousand, eight hundred eighty-seven".