21456887 has 2 divisors, whose sum is σ = 21456888. Its totient is φ = 21456886.

The previous prime is 21456881. The next prime is 21456889. The reversal of 21456887 is 78865412.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21456887 is a prime.

Together with 21456889, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21456881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728443 + 10728444.

It is an arithmetic number, because the mean of its divisors is an integer number (10728444).

Almost surely, 2^21456887 is an apocalyptic number.

21456887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21456887 is an equidigital number, since it uses as much as digits as its factorization.

21456887 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 107520, while the sum is 41.

The square root of 21456887 is about 4632.1579204513. The cubic root of 21456887 is about 277.8789002080.

The spelling of 21456887 in words is "twenty-one million, four hundred fifty-six thousand, eight hundred eighty-seven".