21865255 has 8 divisors (see below), whose sum is σ = 26509392. Its totient is φ = 17311488.

The previous prime is 21865243. The next prime is 21865279. The reversal of 21865255 is 55256812.

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

It is a cyclic number.

It is not a de Polignac number, because 21865255 - 2¹³ = 21857063 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 21865255.

It is a congruent number.

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, 22057 + ... + 23026.

It is an arithmetic number, because the mean of its divisors is an integer number (3313674).

Almost surely, 2^21865255 is an apocalyptic number.

21865255 is a deficient number, since it is larger than the sum of its proper divisors (4644137).

21865255 is an equidigital number, since it uses as much as digits as its factorization.

21865255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45185.

The product of its digits is 24000, while the sum is 34.

The square root of 21865255 is about 4676.0298330956. The cubic root of 21865255 is about 279.6306993566.

The spelling of 21865255 in words is "twenty-one million, eight hundred sixty-five thousand, two hundred fifty-five".