21066865 has 8 divisors (see below), whose sum is σ = 25339968. Its totient is φ = 16813680.

The previous prime is 21066863. The next prime is 21066931. The reversal of 21066865 is 56866012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21066865 - 2¹ = 21066863 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 21066865.

It is not an unprimeable number, because it can be changed into a prime (21066863) 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 7 ways as a sum of consecutive naturals, for example, 2541 + ... + 6970.

It is an arithmetic number, because the mean of its divisors is an integer number (3167496).

Almost surely, 2^21066865 is an apocalyptic number.

It is an amenable number.

21066865 is a deficient number, since it is larger than the sum of its proper divisors (4273103).

21066865 is an equidigital number, since it uses as much as digits as its factorization.

21066865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9959.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 21066865 is about 4589.8654664380. The cubic root of 21066865 is about 276.1849256028.

The spelling of 21066865 in words is "twenty-one million, sixty-six thousand, eight hundred sixty-five".