21381239 has 8 divisors (see below), whose sum is σ = 23358720. Its totient is φ = 19409400.

The previous prime is 21381211. The next prime is 21381259. The reversal of 21381239 is 93218312.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21381239 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12752 + ... + 14330.

It is an arithmetic number, because the mean of its divisors is an integer number (2919840).

Almost surely, 2^21381239 is an apocalyptic number.

21381239 is a deficient number, since it is larger than the sum of its proper divisors (1977481).

21381239 is a wasteful number, since it uses less digits than its factorization.

21381239 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2821.

The product of its digits is 2592, while the sum is 29.

The square root of 21381239 is about 4623.9851859624. The cubic root of 21381239 is about 277.5519541282.

The spelling of 21381239 in words is "twenty-one million, three hundred eighty-one thousand, two hundred thirty-nine".