21116905 has 4 divisors (see below), whose sum is σ = 25340292. Its totient is φ = 16893520.

The previous prime is 21116861. The next prime is 21116911. The reversal of 21116905 is 50961112.

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 10067929 + 11048976 = 3173^2 + 3324^2 .

It is not a de Polignac number, because 21116905 - 2⁹ = 21116393 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 21116905.

It is an unprimeable number.

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, 2111686 + ... + 2111695.

It is an arithmetic number, because the mean of its divisors is an integer number (6335073).

Almost surely, 2^21116905 is an apocalyptic number.

It is an amenable number.

21116905 is a deficient number, since it is larger than the sum of its proper divisors (4223387).

21116905 is an equidigital number, since it uses as much as digits as its factorization.

21116905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4223386.

The product of its (nonzero) digits is 540, while the sum is 25.

The square root of 21116905 is about 4595.3133734273. The cubic root of 21116905 is about 276.4034261672.

The spelling of 21116905 in words is "twenty-one million, one hundred sixteen thousand, nine hundred five".