21866587 has 4 divisors (see below), whose sum is σ = 23017480. Its totient is φ = 20715696.

The previous prime is 21866567. The next prime is 21866597. The reversal of 21866587 is 78566812.

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 21866587 - 2⁷ = 21866459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21866527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 575418 + ... + 575455.

It is an arithmetic number, because the mean of its divisors is an integer number (5754370).

Almost surely, 2^21866587 is an apocalyptic number.

21866587 is a deficient number, since it is larger than the sum of its proper divisors (1150893).

21866587 is a wasteful number, since it uses less digits than its factorization.

21866587 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1150892.

The product of its digits is 161280, while the sum is 43.

The square root of 21866587 is about 4676.1722594447. The cubic root of 21866587 is about 279.6363774751.

The spelling of 21866587 in words is "twenty-one million, eight hundred sixty-six thousand, five hundred eighty-seven".