21867665 has 4 divisors (see below), whose sum is σ = 26241204. Its totient is φ = 17494128.

The previous prime is 21867649. The next prime is 21867673. The reversal of 21867665 is 56676812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15737089 + 6130576 = 3967^2 + 2476^2 .

It is a cyclic number.

It is not a de Polignac number, because 21867665 - 2⁴ = 21867649 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2186762 + ... + 2186771.

It is an arithmetic number, because the mean of its divisors is an integer number (6560301).

Almost surely, 2^21867665 is an apocalyptic number.

It is an amenable number.

21867665 is a deficient number, since it is larger than the sum of its proper divisors (4373539).

21867665 is an equidigital number, since it uses as much as digits as its factorization.

21867665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4373538.

The product of its digits is 120960, while the sum is 41.

The square root of 21867665 is about 4676.2875232389. The cubic root of 21867665 is about 279.6409726605.

The spelling of 21867665 in words is "twenty-one million, eight hundred sixty-seven thousand, six hundred sixty-five".