21384865 has 4 divisors (see below), whose sum is σ = 25661844. Its totient is φ = 17107888.

The previous prime is 21384841. The next prime is 21384877. The reversal of 21384865 is 56848312.

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 3845521 + 17539344 = 1961^2 + 4188^2 .

It is a cyclic number.

It is not a de Polignac number, because 21384865 - 2⁹ = 21384353 is a prime.

It is a Duffinian number.

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, 2138482 + ... + 2138491.

It is an arithmetic number, because the mean of its divisors is an integer number (6415461).

Almost surely, 2^21384865 is an apocalyptic number.

It is an amenable number.

21384865 is a deficient number, since it is larger than the sum of its proper divisors (4276979).

21384865 is an equidigital number, since it uses as much as digits as its factorization.

21384865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4276978.

The product of its digits is 46080, while the sum is 37.

The square root of 21384865 is about 4624.3772553718. The cubic root of 21384865 is about 277.5676430615.

It can be divided in two parts, 213 and 84865, that added together give a triangular number (85078 = T₄₁₂).

The spelling of 21384865 in words is "twenty-one million, three hundred eighty-four thousand, eight hundred sixty-five".