21842539 has 4 divisors (see below), whose sum is σ = 22595760. Its totient is φ = 21089320.

The previous prime is 21842521. The next prime is 21842551. The reversal of 21842539 is 93524812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21842539 - 2⁹ = 21842027 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21842239) 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, 376567 + ... + 376624.

It is an arithmetic number, because the mean of its divisors is an integer number (5648940).

Almost surely, 2^21842539 is an apocalyptic number.

21842539 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21842539 is a deficient number, since it is larger than the sum of its proper divisors (753221).

21842539 is an equidigital number, since it uses as much as digits as its factorization.

21842539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 753220.

The product of its digits is 17280, while the sum is 34.

The square root of 21842539 is about 4673.6002182472. The cubic root of 21842539 is about 279.5338288958.

The spelling of 21842539 in words is "twenty-one million, eight hundred forty-two thousand, five hundred thirty-nine".