21036305 has 4 divisors (see below), whose sum is σ = 25243572. Its totient is φ = 16829040.

The previous prime is 21036299. The next prime is 21036311. The reversal of 21036305 is 50363012.

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

It is an interprime number because it is at equal distance from previous prime (21036299) and next prime (21036311).

It can be written as a sum of positive squares in 2 ways, for example, as 16248961 + 4787344 = 4031^2 + 2188^2 .

It is not a de Polignac number, because 21036305 - 2⁴ = 21036289 is a prime.

It is a super-2 number, since 2×21036305² = 885052256106050, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

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, 2103626 + ... + 2103635.

It is an arithmetic number, because the mean of its divisors is an integer number (6310893).

Almost surely, 2^21036305 is an apocalyptic number.

It is an amenable number.

21036305 is a deficient number, since it is larger than the sum of its proper divisors (4207267).

21036305 is an equidigital number, since it uses as much as digits as its factorization.

21036305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4207266.

The product of its (nonzero) digits is 540, while the sum is 20.

The square root of 21036305 is about 4586.5351846465. The cubic root of 21036305 is about 276.0513145855.

Adding to 21036305 its reverse (50363012), we get a palindrome (71399317).

The spelling of 21036305 in words is "twenty-one million, thirty-six thousand, three hundred five".