21538519 has 2 divisors, whose sum is σ = 21538520. Its totient is φ = 21538518.

The previous prime is 21538499. The next prime is 21538523. The reversal of 21538519 is 91583512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21538519 - 2⁵ = 21538487 is a prime.

It is a super-2 number, since 2×21538519² = 927815601426722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21538579) 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 as a sum of consecutive naturals, namely, 10769259 + 10769260.

It is an arithmetic number, because the mean of its divisors is an integer number (10769260).

Almost surely, 2^21538519 is an apocalyptic number.

21538519 is a deficient number, since it is larger than the sum of its proper divisors (1).

21538519 is an equidigital number, since it uses as much as digits as its factorization.

21538519 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10800, while the sum is 34.

The square root of 21538519 is about 4640.9609996207. The cubic root of 21538519 is about 278.2308478823.

The spelling of 21538519 in words is "twenty-one million, five hundred thirty-eight thousand, five hundred nineteen".