21084239 has 4 divisors (see below), whose sum is σ = 23001000. Its totient is φ = 19167480.

The previous prime is 21084227. The next prime is 21084253. The reversal of 21084239 is 93248012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21084239 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21084269) 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, 958364 + ... + 958385.

It is an arithmetic number, because the mean of its divisors is an integer number (5750250).

Almost surely, 2^21084239 is an apocalyptic number.

21084239 is a deficient number, since it is larger than the sum of its proper divisors (1916761).

21084239 is a wasteful number, since it uses less digits than its factorization.

21084239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1916760.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21084239 is about 4591.7577244450. The cubic root of 21084239 is about 276.2608286604.

The spelling of 21084239 in words is "twenty-one million, eighty-four thousand, two hundred thirty-nine".