21378585 has 16 divisors (see below), whose sum is σ = 34640640. Its totient is φ = 11256960.

The previous prime is 21378547. The next prime is 21378587. The reversal of 21378585 is 58587312.

It is not a de Polignac number, because 21378585 - 2⁶ = 21378521 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21378587) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 7836 + ... + 10205.

It is an arithmetic number, because the mean of its divisors is an integer number (2165040).

Almost surely, 2^21378585 is an apocalyptic number.

It is an amenable number.

21378585 is a deficient number, since it is larger than the sum of its proper divisors (13262055).

21378585 is a wasteful number, since it uses less digits than its factorization.

21378585 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18128.

The product of its digits is 67200, while the sum is 39.

The square root of 21378585 is about 4623.6981951680. The cubic root of 21378585 is about 277.5404697085.

The spelling of 21378585 in words is "twenty-one million, three hundred seventy-eight thousand, five hundred eighty-five".