21284839 has 2 divisors, whose sum is σ = 21284840. Its totient is φ = 21284838.

The previous prime is 21284801. The next prime is 21284903. The reversal of 21284839 is 93848212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21284839 - 2¹¹ = 21282791 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21284798 and 21284807.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21284339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10642419 + 10642420.

It is an arithmetic number, because the mean of its divisors is an integer number (10642420).

Almost surely, 2^21284839 is an apocalyptic number.

21284839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21284839 is an equidigital number, since it uses as much as digits as its factorization.

21284839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27648, while the sum is 37.

The square root of 21284839 is about 4613.5495011975. The cubic root of 21284839 is about 277.1341997230.

The spelling of 21284839 in words is "twenty-one million, two hundred eighty-four thousand, eight hundred thirty-nine".