21542839 has 4 divisors (see below), whose sum is σ = 21700224. Its totient is φ = 21385456.

The previous prime is 21542837. The next prime is 21542849. The reversal of 21542839 is 93824512.

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 21542839 - 2¹ = 21542837 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542831) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 78487 + ... + 78760.

It is an arithmetic number, because the mean of its divisors is an integer number (5425056).

Almost surely, 2^21542839 is an apocalyptic number.

21542839 is a deficient number, since it is larger than the sum of its proper divisors (157385).

21542839 is a wasteful number, since it uses less digits than its factorization.

21542839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157384.

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

The square root of 21542839 is about 4641.4263971327. The cubic root of 21542839 is about 278.2494483087.

The spelling of 21542839 in words is "twenty-one million, five hundred forty-two thousand, eight hundred thirty-nine".