21284291 has 4 divisors (see below), whose sum is σ = 24324912. Its totient is φ = 18243672.

The previous prime is 21284281. The next prime is 21284299. The reversal of 21284291 is 19248212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21284291 - 2⁶ = 21284227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21284299) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1520300 + ... + 1520313.

It is an arithmetic number, because the mean of its divisors is an integer number (6081228).

Almost surely, 2^21284291 is an apocalyptic number.

21284291 is a deficient number, since it is larger than the sum of its proper divisors (3040621).

21284291 is an equidigital number, since it uses as much as digits as its factorization.

21284291 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3040620.

The product of its digits is 2304, while the sum is 29.

The square root of 21284291 is about 4613.4901105345. The cubic root of 21284291 is about 277.1318213345.

The spelling of 21284291 in words is "twenty-one million, two hundred eighty-four thousand, two hundred ninety-one".