21078239 has 32 divisors (see below), whose sum is σ = 27847680. Its totient is φ = 15489792.

The previous prime is 21078209. The next prime is 21078257. The reversal of 21078239 is 93287012.

It is a cyclic number.

It is not a de Polignac number, because 21078239 - 2²⁰ = 20029663 is a prime.

It is a super-2 number, since 2×21078239² = 888584318682242, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21078209) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 126134 + ... + 126300.

It is an arithmetic number, because the mean of its divisors is an integer number (870240).

Almost surely, 2^21078239 is an apocalyptic number.

21078239 is a deficient number, since it is larger than the sum of its proper divisors (6769441).

21078239 is a wasteful number, since it uses less digits than its factorization.

21078239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 21078239 is about 4591.1043333821. The cubic root of 21078239 is about 276.2346207391.

The spelling of 21078239 in words is "twenty-one million, seventy-eight thousand, two hundred thirty-nine".