21865687 has 2 divisors, whose sum is σ = 21865688. Its totient is φ = 21865686.

The previous prime is 21865661. The next prime is 21865721. The reversal of 21865687 is 78656812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21865687 - 2⁷ = 21865559 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21265687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932843 + 10932844.

It is an arithmetic number, because the mean of its divisors is an integer number (10932844).

Almost surely, 2^21865687 is an apocalyptic number.

21865687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21865687 is an equidigital number, since it uses as much as digits as its factorization.

21865687 is an evil number, because the sum of its binary digits is even.

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

The square root of 21865687 is about 4676.0760259003. The cubic root of 21865687 is about 279.6325409338.

The spelling of 21865687 in words is "twenty-one million, eight hundred sixty-five thousand, six hundred eighty-seven".