21580513 has 2 divisors, whose sum is σ = 21580514. Its totient is φ = 21580512.

The previous prime is 21580511. The next prime is 21580529. The reversal of 21580513 is 31508512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20903184 + 677329 = 4572^2 + 823^2 .

It is a cyclic number.

It is not a de Polignac number, because 21580513 - 2¹ = 21580511 is a prime.

Together with 21580511, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21580511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10790256 + 10790257.

It is an arithmetic number, because the mean of its divisors is an integer number (10790257).

Almost surely, 2^21580513 is an apocalyptic number.

It is an amenable number.

21580513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21580513 is an equidigital number, since it uses as much as digits as its factorization.

21580513 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1200, while the sum is 25.

The square root of 21580513 is about 4645.4830749880. The cubic root of 21580513 is about 278.4115542241.

The spelling of 21580513 in words is "twenty-one million, five hundred eighty thousand, five hundred thirteen".