21668039 has 8 divisors (see below), whose sum is σ = 22420608. Its totient is φ = 20918880.

The previous prime is 21668033. The next prime is 21668099. The reversal of 21668039 is 93086612.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21668039 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668033) 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, 24269 + ... + 25145.

It is an arithmetic number, because the mean of its divisors is an integer number (2802576).

Almost surely, 2^21668039 is an apocalyptic number.

21668039 is a deficient number, since it is larger than the sum of its proper divisors (752569).

21668039 is an equidigital number, since it uses as much as digits as its factorization.

21668039 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1705.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21668039 is about 4654.8940911690. The cubic root of 21668039 is about 278.7874393196.

The spelling of 21668039 in words is "twenty-one million, six hundred sixty-eight thousand, thirty-nine".