21663985 has 8 divisors (see below), whose sum is σ = 29710656. Its totient is φ = 14855280.

The previous prime is 21663979. The next prime is 21663989. The reversal of 21663985 is 58936612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21663985 - 2³ = 21663977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21663989) 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 in 7 ways as a sum of consecutive naturals, for example, 309451 + ... + 309520.

It is an arithmetic number, because the mean of its divisors is an integer number (3713832).

Almost surely, 2^21663985 is an apocalyptic number.

It is an amenable number.

21663985 is a deficient number, since it is larger than the sum of its proper divisors (8046671).

21663985 is an equidigital number, since it uses as much as digits as its factorization.

21663985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 618983.

The product of its digits is 77760, while the sum is 40.

The square root of 21663985 is about 4654.4586151345. The cubic root of 21663985 is about 278.7700515783.

The spelling of 21663985 in words is "twenty-one million, six hundred sixty-three thousand, nine hundred eighty-five".