21668857399 has 16 divisors (see below), whose sum is σ = 25132474368. Its totient is φ = 18297842112.

The previous prime is 21668857387. The next prime is 21668857409. The reversal of 21668857399 is 99375886612.

It is a cyclic number.

It is not a de Polignac number, because 21668857399 - 2⁵ = 21668857367 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21668857399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668857319) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 429354 + ... + 477160.

It is an arithmetic number, because the mean of its divisors is an integer number (1570779648).

Almost surely, 2^21668857399 is an apocalyptic number.

21668857399 is a deficient number, since it is larger than the sum of its proper divisors (3463616969).

21668857399 is an equidigital number, since it uses as much as digits as its factorization.

21668857399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48774.

The product of its digits is 39191040, while the sum is 64.

The spelling of 21668857399 in words is "twenty-one billion, six hundred sixty-eight million, eight hundred fifty-seven thousand, three hundred ninety-nine".