21856487 has 2 divisors, whose sum is σ = 21856488. Its totient is φ = 21856486.

The previous prime is 21856469. The next prime is 21856537. The reversal of 21856487 is 78465812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21856487 - 2⁶ = 21856423 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21856987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10928243 + 10928244.

It is an arithmetic number, because the mean of its divisors is an integer number (10928244).

Almost surely, 2^21856487 is an apocalyptic number.

21856487 is a deficient number, since it is larger than the sum of its proper divisors (1).

21856487 is an equidigital number, since it uses as much as digits as its factorization.

21856487 is an evil number, because the sum of its binary digits is even.

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

The square root of 21856487 is about 4675.0921916044. The cubic root of 21856487 is about 279.5933169163.

The spelling of 21856487 in words is "twenty-one million, eight hundred fifty-six thousand, four hundred eighty-seven".