21855867 has 12 divisors (see below), whose sum is σ = 32031720. Its totient is φ = 13245760.

The previous prime is 21855839. The next prime is 21855877. The reversal of 21855867 is 76855812.

It is not a de Polignac number, because 21855867 - 2⁶ = 21855803 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21855817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29742 + ... + 30467.

It is an arithmetic number, because the mean of its divisors is an integer number (2669310).

Almost surely, 2^21855867 is an apocalyptic number.

21855867 is a deficient number, since it is larger than the sum of its proper divisors (10175853).

21855867 is a wasteful number, since it uses less digits than its factorization.

21855867 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60234 (or 60223 counting only the distinct ones).

The product of its digits is 134400, while the sum is 42.

The square root of 21855867 is about 4675.0258822813. The cubic root of 21855867 is about 279.5906731627.

Subtracting 21855867 from its reverse (76855812), we obtain a palindrome (54999945).

It can be divided in two parts, 21855 and 867, that added together give a palindrome (22722).

The spelling of 21855867 in words is "twenty-one million, eight hundred fifty-five thousand, eight hundred sixty-seven".