21041305 has 4 divisors (see below), whose sum is σ = 25249572. Its totient is φ = 16833040.

The previous prime is 21041299. The next prime is 21041309. The reversal of 21041305 is 50314012.

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 2611456 + 18429849 = 1616^2 + 4293^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21041305 is a prime.

It is a super-2 number, since 2×21041305² = 885473032206050, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21041309) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2104126 + ... + 2104135.

It is an arithmetic number, because the mean of its divisors is an integer number (6312393).

Almost surely, 2^21041305 is an apocalyptic number.

It is an amenable number.

21041305 is a deficient number, since it is larger than the sum of its proper divisors (4208267).

21041305 is an equidigital number, since it uses as much as digits as its factorization.

21041305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4208266.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21041305 is about 4587.0802260261. The cubic root of 21041305 is about 276.0731838765.

Adding to 21041305 its reverse (50314012), we get a palindrome (71355317).

The spelling of 21041305 in words is "twenty-one million, forty-one thousand, three hundred five".