21041813 has 4 divisors (see below), whose sum is σ = 22660428. Its totient is φ = 19423200.

The previous prime is 21041807. The next prime is 21041821. The reversal of 21041813 is 31814012.

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 2439844 + 18601969 = 1562^2 + 4313^2 .

It is a cyclic number.

It is not a de Polignac number, because 21041813 - 2²⁴ = 4264597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21041213) 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, 809288 + ... + 809313.

It is an arithmetic number, because the mean of its divisors is an integer number (5665107).

Almost surely, 2^21041813 is an apocalyptic number.

It is an amenable number.

21041813 is a deficient number, since it is larger than the sum of its proper divisors (1618615).

21041813 is a wasteful number, since it uses less digits than its factorization.

21041813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1618614.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21041813 is about 4587.1355986062. The cubic root of 21041813 is about 276.0754056026.

Adding to 21041813 its reverse (31814012), we get a palindrome (52855825).

The spelling of 21041813 in words is "twenty-one million, forty-one thousand, eight hundred thirteen".