21538839 has 8 divisors (see below), whose sum is σ = 32821120. Its totient is φ = 12307896.

The previous prime is 21538789. The next prime is 21538841. The reversal of 21538839 is 93883512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21538839 - 2¹¹ = 21536791 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21538797 and 21538806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538849) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 512809 + ... + 512850.

It is an arithmetic number, because the mean of its divisors is an integer number (4102640).

Almost surely, 2^21538839 is an apocalyptic number.

21538839 is a deficient number, since it is larger than the sum of its proper divisors (11282281).

21538839 is a wasteful number, since it uses less digits than its factorization.

21538839 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1025669.

The product of its digits is 51840, while the sum is 39.

The square root of 21538839 is about 4640.9954751109. The cubic root of 21538839 is about 278.2322257770.

The spelling of 21538839 in words is "twenty-one million, five hundred thirty-eight thousand, eight hundred thirty-nine".