21040321 has 4 divisors (see below), whose sum is σ = 21050452. Its totient is φ = 21030192.

The previous prime is 21040297. The next prime is 21040387. The reversal of 21040321 is 12304012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 19927296 + 1113025 = 4464^2 + 1055^2 .

It is a cyclic number.

It is not a de Polignac number, because 21040321 - 2¹¹ = 21038273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21040121) 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, 690 + ... + 6523.

It is an arithmetic number, because the mean of its divisors is an integer number (5262613).

Almost surely, 2^21040321 is an apocalyptic number.

It is an amenable number.

21040321 is a deficient number, since it is larger than the sum of its proper divisors (10131).

21040321 is an equidigital number, since it uses as much as digits as its factorization.

21040321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10130.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21040321 is about 4586.9729670012. The cubic root of 21040321 is about 276.0688802739.

Adding to 21040321 its reverse (12304012), we get a palindrome (33344333).

The spelling of 21040321 in words is "twenty-one million, forty thousand, three hundred twenty-one".