21108481 has 4 divisors (see below), whose sum is σ = 21623364. Its totient is φ = 20593600.

The previous prime is 21108431. The next prime is 21108497. The reversal of 21108481 is 18480112.

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 6170256 + 14938225 = 2484^2 + 3865^2 .

It is a cyclic number.

It is not a de Polignac number, because 21108481 - 2¹⁵ = 21075713 is a prime.

It is a super-2 number, since 2×21108481² = 891135940254722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21108431) 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, 257380 + ... + 257461.

It is an arithmetic number, because the mean of its divisors is an integer number (5405841).

Almost surely, 2^21108481 is an apocalyptic number.

It is an amenable number.

21108481 is a deficient number, since it is larger than the sum of its proper divisors (514883).

21108481 is an equidigital number, since it uses as much as digits as its factorization.

21108481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 514882.

The product of its (nonzero) digits is 512, while the sum is 25.

The square root of 21108481 is about 4594.3966959765. The cubic root of 21108481 is about 276.3666668007.

Adding to 21108481 its reverse (18480112), we get a palindrome (39588593).

The spelling of 21108481 in words is "twenty-one million, one hundred eight thousand, four hundred eighty-one".