21385985 has 4 divisors (see below), whose sum is σ = 25663188. Its totient is φ = 17108784.

The previous prime is 21385967. The next prime is 21385999. The reversal of 21385985 is 58958312.

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 11343424 + 10042561 = 3368^2 + 3169^2 .

It is a cyclic number.

It is not a de Polignac number, because 21385985 - 2¹⁸ = 21123841 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2138594 + ... + 2138603.

It is an arithmetic number, because the mean of its divisors is an integer number (6415797).

Almost surely, 2^21385985 is an apocalyptic number.

It is an amenable number.

21385985 is a deficient number, since it is larger than the sum of its proper divisors (4277203).

21385985 is an equidigital number, since it uses as much as digits as its factorization.

21385985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4277202.

The product of its digits is 86400, while the sum is 41.

The square root of 21385985 is about 4624.4983511728. The cubic root of 21385985 is about 277.5724887056.

The spelling of 21385985 in words is "twenty-one million, three hundred eighty-five thousand, nine hundred eighty-five".