21478339 has 2 divisors, whose sum is σ = 21478340. Its totient is φ = 21478338.

The previous prime is 21478337. The next prime is 21478351. The reversal of 21478339 is 93387412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21478339 - 2¹ = 21478337 is a prime.

It is a super-2 number, since 2×21478339² = 922638092397842, which contains 22 as substring.

Together with 21478337, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21478298 and 21478307.

It is not a weakly prime, because it can be changed into another prime (21478333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10739169 + 10739170.

It is an arithmetic number, because the mean of its divisors is an integer number (10739170).

Almost surely, 2^21478339 is an apocalyptic number.

21478339 is a deficient number, since it is larger than the sum of its proper divisors (1).

21478339 is an equidigital number, since it uses as much as digits as its factorization.

21478339 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 37.

The square root of 21478339 is about 4634.4728934367. The cubic root of 21478339 is about 277.9714745674.

The spelling of 21478339 in words is "twenty-one million, four hundred seventy-eight thousand, three hundred thirty-nine".