21865345 has 4 divisors (see below), whose sum is σ = 26238420. Its totient is φ = 17492272.

The previous prime is 21865339. The next prime is 21865351. The reversal of 21865345 is 54356812.

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

It is an interprime number because it is at equal distance from previous prime (21865339) and next prime (21865351).

It can be written as a sum of positive squares in 2 ways, for example, as 13593969 + 8271376 = 3687^2 + 2876^2 .

It is a cyclic number.

It is not a de Polignac number, because 21865345 - 2¹¹ = 21863297 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21865345.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2186530 + ... + 2186539.

It is an arithmetic number, because the mean of its divisors is an integer number (6559605).

Almost surely, 2^21865345 is an apocalyptic number.

It is an amenable number.

21865345 is a deficient number, since it is larger than the sum of its proper divisors (4373075).

21865345 is an equidigital number, since it uses as much as digits as its factorization.

21865345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4373074.

The product of its digits is 28800, while the sum is 34.

The square root of 21865345 is about 4676.0394566342. The cubic root of 21865345 is about 279.6310830205.

The spelling of 21865345 in words is "twenty-one million, eight hundred sixty-five thousand, three hundred forty-five".