21278459 has 2 divisors, whose sum is σ = 21278460. Its totient is φ = 21278458.

The previous prime is 21278449. The next prime is 21278471. The reversal of 21278459 is 95487212.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21278459 is a prime.

It is not a weakly prime, because it can be changed into another prime (21278419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639229 + 10639230.

It is an arithmetic number, because the mean of its divisors is an integer number (10639230).

Almost surely, 2^21278459 is an apocalyptic number.

21278459 is a deficient number, since it is larger than the sum of its proper divisors (1).

21278459 is an equidigital number, since it uses as much as digits as its factorization.

21278459 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 40320, while the sum is 38.

The square root of 21278459 is about 4612.8580077865. The cubic root of 21278459 is about 277.1065071968.

The spelling of 21278459 in words is "twenty-one million, two hundred seventy-eight thousand, four hundred fifty-nine".