21860665 has 4 divisors (see below), whose sum is σ = 26232804. Its totient is φ = 17488528.

The previous prime is 21860651. The next prime is 21860689. The reversal of 21860665 is 56606812.

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 6012304 + 15848361 = 2452^2 + 3981^2 .

It is a cyclic number.

It is not a de Polignac number, because 21860665 - 2¹³ = 21852473 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 21860665.

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, 2186062 + ... + 2186071.

It is an arithmetic number, because the mean of its divisors is an integer number (6558201).

Almost surely, 2^21860665 is an apocalyptic number.

It is an amenable number.

21860665 is a deficient number, since it is larger than the sum of its proper divisors (4372139).

21860665 is an equidigital number, since it uses as much as digits as its factorization.

21860665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4372138.

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

The square root of 21860665 is about 4675.5390063607. The cubic root of 21860665 is about 279.6111311005.

The spelling of 21860665 in words is "twenty-one million, eight hundred sixty thousand, six hundred sixty-five".