21330517 has 4 divisors (see below), whose sum is σ = 22971340. Its totient is φ = 19689696.

The previous prime is 21330503. The next prime is 21330581. The reversal of 21330517 is 71503312.

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 7447441 + 13883076 = 2729^2 + 3726^2 .

It is not a de Polignac number, because 21330517 - 2²³ = 12941909 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 (21330817) by changing a digit.

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, 820392 + ... + 820417.

It is an arithmetic number, because the mean of its divisors is an integer number (5742835).

Almost surely, 2^21330517 is an apocalyptic number.

It is an amenable number.

21330517 is a deficient number, since it is larger than the sum of its proper divisors (1640823).

21330517 is a wasteful number, since it uses less digits than its factorization.

21330517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1640822.

The product of its (nonzero) digits is 630, while the sum is 22.

The square root of 21330517 is about 4618.4972664277. The cubic root of 21330517 is about 277.3323046002.

Adding to 21330517 its reverse (71503312), we get a palindrome (92833829).

The spelling of 21330517 in words is "twenty-one million, three hundred thirty thousand, five hundred seventeen".