21385915 has 16 divisors (see below), whose sum is σ = 27293760. Its totient is φ = 16030720.

The previous prime is 21385891. The next prime is 21385937. The reversal of 21385915 is 51958312.

It is not a de Polignac number, because 21385915 - 2¹¹ = 21383867 is a prime.

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 15 ways as a sum of consecutive naturals, for example, 26031 + ... + 26839.

It is an arithmetic number, because the mean of its divisors is an integer number (1705860).

Almost surely, 2^21385915 is an apocalyptic number.

21385915 is a deficient number, since it is larger than the sum of its proper divisors (5907845).

21385915 is a wasteful number, since it uses less digits than its factorization.

21385915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1142.

The product of its digits is 10800, while the sum is 34.

The square root of 21385915 is about 4624.4907827781. The cubic root of 21385915 is about 277.5721858578.

The spelling of 21385915 in words is "twenty-one million, three hundred eighty-five thousand, nine hundred fifteen".