21120305 has 12 divisors (see below), whose sum is σ = 26750772. Its totient is φ = 16005600.

The previous prime is 21120283. The next prime is 21120311. The reversal of 21120305 is 50302112.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 12222016 + 8898289 = 3496^2 + 2983^2 .

It is not a de Polignac number, because 21120305 - 2¹² = 21116209 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21120305.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4046 + ... + 7655.

It is an arithmetic number, because the mean of its divisors is an integer number (2229231).

Almost surely, 2^21120305 is an apocalyptic number.

It is an amenable number.

21120305 is a deficient number, since it is larger than the sum of its proper divisors (5630467).

21120305 is a wasteful number, since it uses less digits than its factorization.

21120305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11744 (or 11725 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21120305 is about 4595.6833006638. The cubic root of 21120305 is about 276.4182597995.

Adding to 21120305 its reverse (50302112), we get a palindrome (71422417).

The spelling of 21120305 in words is "twenty-one million, one hundred twenty thousand, three hundred five".