21864659 has 2 divisors, whose sum is σ = 21864660. Its totient is φ = 21864658.

The previous prime is 21864653. The next prime is 21864757. The reversal of 21864659 is 95646812.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21864659 - 2¹⁶ = 21799123 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21864653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932329 + 10932330.

It is an arithmetic number, because the mean of its divisors is an integer number (10932330).

Almost surely, 2^21864659 is an apocalyptic number.

21864659 is a deficient number, since it is larger than the sum of its proper divisors (1).

21864659 is an equidigital number, since it uses as much as digits as its factorization.

21864659 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 41.

The square root of 21864659 is about 4675.9661033844. The cubic root of 21864659 is about 279.6281586223.

The spelling of 21864659 in words is "twenty-one million, eight hundred sixty-four thousand, six hundred fifty-nine".