21856867 has 2 divisors, whose sum is σ = 21856868. Its totient is φ = 21856866.

The previous prime is 21856847. The next prime is 21856873. The reversal of 21856867 is 76865812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21856867 - 2¹⁹ = 21332579 is a prime.

It is not a weakly prime, because it can be changed into another prime (21856817) 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 as a sum of consecutive naturals, namely, 10928433 + 10928434.

It is an arithmetic number, because the mean of its divisors is an integer number (10928434).

Almost surely, 2^21856867 is an apocalyptic number.

21856867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21856867 is an equidigital number, since it uses as much as digits as its factorization.

21856867 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 161280, while the sum is 43.

The square root of 21856867 is about 4675.1328323375. The cubic root of 21856867 is about 279.5949372567.

The spelling of 21856867 in words is "twenty-one million, eight hundred fifty-six thousand, eight hundred sixty-seven".