21036685 has 4 divisors (see below), whose sum is σ = 25244028. Its totient is φ = 16829344.

The previous prime is 21036671. The next prime is 21036689. The reversal of 21036685 is 58663012.

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 13089924 + 7946761 = 3618^2 + 2819^2 .

It is a cyclic number.

It is not a de Polignac number, because 21036685 - 2¹³ = 21028493 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21036689) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2103664 + ... + 2103673.

It is an arithmetic number, because the mean of its divisors is an integer number (6311007).

Almost surely, 2^21036685 is an apocalyptic number.

It is an amenable number.

21036685 is a deficient number, since it is larger than the sum of its proper divisors (4207343).

21036685 is an equidigital number, since it uses as much as digits as its factorization.

21036685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4207342.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 21036685 is about 4586.5766100655. The cubic root of 21036685 is about 276.0529767733.

Adding to 21036685 its reverse (58663012), we get a palindrome (79699697).

The spelling of 21036685 in words is "twenty-one million, thirty-six thousand, six hundred eighty-five".