21284687 has 2 divisors, whose sum is σ = 21284688. Its totient is φ = 21284686.

The previous prime is 21284677. The next prime is 21284689. The reversal of 21284687 is 78648212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21284687 - 2⁴ = 21284671 is a prime.

Together with 21284689, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21284687.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21284689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10642343 + 10642344.

It is an arithmetic number, because the mean of its divisors is an integer number (10642344).

Almost surely, 2^21284687 is an apocalyptic number.

21284687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21284687 is an equidigital number, since it uses as much as digits as its factorization.

21284687 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43008, while the sum is 38.

The square root of 21284687 is about 4613.5330279516. The cubic root of 21284687 is about 277.1335400281.

The spelling of 21284687 in words is "twenty-one million, two hundred eighty-four thousand, six hundred eighty-seven".