21006835 has 4 divisors (see below), whose sum is σ = 25208208. Its totient is φ = 16805464.

The previous prime is 21006829. The next prime is 21006847. The reversal of 21006835 is 53860012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21006835 - 2⁵ = 21006803 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, 2100679 + ... + 2100688.

It is an arithmetic number, because the mean of its divisors is an integer number (6302052).

Almost surely, 2^21006835 is an apocalyptic number.

21006835 is a deficient number, since it is larger than the sum of its proper divisors (4201373).

21006835 is an equidigital number, since it uses as much as digits as its factorization.

21006835 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4201372.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21006835 is about 4583.3213939238. The cubic root of 21006835 is about 275.9223465290.

Adding to 21006835 its reverse (53860012), we get a palindrome (74866847).

The spelling of 21006835 in words is "twenty-one million, six thousand, eight hundred thirty-five".