21018239 has 8 divisors (see below), whose sum is σ = 24277968. Its totient is φ = 17983360.

The previous prime is 21018229. The next prime is 21018241. The reversal of 21018239 is 93281012.

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

It is a cyclic number.

It is not a de Polignac number, because 21018239 - 2²⁴ = 4241023 is a prime.

It is a super-2 number, since 2×21018239² = 883532741322242, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018229) 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, 56012 + ... + 56385.

It is an arithmetic number, because the mean of its divisors is an integer number (3034746).

Almost surely, 2^21018239 is an apocalyptic number.

21018239 is a deficient number, since it is larger than the sum of its proper divisors (3259729).

21018239 is a wasteful number, since it uses less digits than its factorization.

21018239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112425.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21018239 is about 4584.5653010945. The cubic root of 21018239 is about 275.9722675699.

The spelling of 21018239 in words is "twenty-one million, eighteen thousand, two hundred thirty-nine".