21128519 has 4 divisors (see below), whose sum is σ = 21140544. Its totient is φ = 21116496.

The previous prime is 21128507. The next prime is 21128539. The reversal of 21128519 is 91582112.

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 is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21128519 is a prime.

It is a super-2 number, since 2×21128519² = 892828630266722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21128491 and 21128500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21128539) 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 in 3 ways as a sum of consecutive naturals, for example, 2807 + ... + 7080.

It is an arithmetic number, because the mean of its divisors is an integer number (5285136).

Almost surely, 2^21128519 is an apocalyptic number.

21128519 is a deficient number, since it is larger than the sum of its proper divisors (12025).

21128519 is an equidigital number, since it uses as much as digits as its factorization.

21128519 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12024.

The product of its digits is 1440, while the sum is 29.

The square root of 21128519 is about 4596.5768785043. The cubic root of 21128519 is about 276.4540895426.

The spelling of 21128519 in words is "twenty-one million, one hundred twenty-eight thousand, five hundred nineteen".