21868505 has 4 divisors (see below), whose sum is σ = 26242212. Its totient is φ = 17494800.

The previous prime is 21868501. The next prime is 21868519. The reversal of 21868505 is 50586812.

It is a happy number.

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 9223369 + 12645136 = 3037^2 + 3556^2 .

It is not a de Polignac number, because 21868505 - 2² = 21868501 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21868501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2186846 + ... + 2186855.

It is an arithmetic number, because the mean of its divisors is an integer number (6560553).

Almost surely, 2^21868505 is an apocalyptic number.

It is an amenable number.

21868505 is a deficient number, since it is larger than the sum of its proper divisors (4373707).

21868505 is an equidigital number, since it uses as much as digits as its factorization.

21868505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4373706.

The product of its (nonzero) digits is 19200, while the sum is 35.

The square root of 21868505 is about 4676.3773372131. The cubic root of 21868505 is about 279.6445532197.

The spelling of 21868505 in words is "twenty-one million, eight hundred sixty-eight thousand, five hundred five".