21280239 has 14 divisors (see below), whose sum is σ = 31906856. Its totient is φ = 14186340.

The previous prime is 21280223. The next prime is 21280241. The reversal of 21280239 is 93208212.

It is a happy number.

It is not a de Polignac number, because 21280239 - 2⁴ = 21280223 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280219) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 13867 + ... + 15324.

Almost surely, 2^21280239 is an apocalyptic number.

21280239 is a deficient number, since it is larger than the sum of its proper divisors (10626617).

21280239 is an frugal number, since it uses more digits than its factorization.

21280239 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29209 (or 29194 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21280239 is about 4613.0509427059. The cubic root of 21280239 is about 277.1142338815.

The spelling of 21280239 in words is "twenty-one million, two hundred eighty thousand, two hundred thirty-nine".