21052105 has 16 divisors (see below), whose sum is σ = 25856784. Its totient is φ = 16450560.

The previous prime is 21052091. The next prime is 21052111. The reversal of 21052105 is 50125012.

It can be written as a sum of positive squares in 8 ways, for example, as 2493241 + 18558864 = 1579^2 + 4308^2 .

It is not a de Polignac number, because 21052105 - 2⁷ = 21051977 is a prime.

It is a super-2 number, since 2×21052105² = 886382249862050, 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 15 ways as a sum of consecutive naturals, for example, 49795 + ... + 50215.

It is an arithmetic number, because the mean of its divisors is an integer number (1616049).

Almost surely, 2^21052105 is an apocalyptic number.

It is an amenable number.

21052105 is a deficient number, since it is larger than the sum of its proper divisors (4804679).

21052105 is a wasteful number, since it uses less digits than its factorization.

21052105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636.

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21052105 is about 4588.2572944420. The cubic root of 21052105 is about 276.1204097244.

Adding to 21052105 its reverse (50125012), we get a palindrome (71177117).

The spelling of 21052105 in words is "twenty-one million, fifty-two thousand, one hundred five".