21818665 has 8 divisors (see below), whose sum is σ = 28562688. Its totient is φ = 15868080.

The previous prime is 21818653. The next prime is 21818711. The reversal of 21818665 is 56681812.

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

It is not a de Polignac number, because 21818665 - 2¹⁷ = 21687593 is a prime.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 198297 + ... + 198406.

It is an arithmetic number, because the mean of its divisors is an integer number (3570336).

Almost surely, 2^21818665 is an apocalyptic number.

It is an amenable number.

21818665 is a deficient number, since it is larger than the sum of its proper divisors (6744023).

21818665 is a wasteful number, since it uses less digits than its factorization.

21818665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396719.

The product of its digits is 23040, while the sum is 37.

The square root of 21818665 is about 4671.0453862064. The cubic root of 21818665 is about 279.4319478289.

The spelling of 21818665 in words is "twenty-one million, eight hundred eighteen thousand, six hundred sixty-five".