21666867217 has 8 divisors (see below), whose sum is σ = 22943210472. Its totient is φ = 20390726400.

The previous prime is 21666867199. The next prime is 21666867239. The reversal of 21666867217 is 71276866612.

It can be written as a sum of positive squares in 4 ways, for example, as 19196379601 + 2470487616 = 138551^2 + 49704^2 .

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-21666867217 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21666867247) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 207367 + ... + 293827.

It is an arithmetic number, because the mean of its divisors is an integer number (2867901309).

Almost surely, 2^21666867217 is an apocalyptic number.

It is an amenable number.

21666867217 is a deficient number, since it is larger than the sum of its proper divisors (1276343255).

21666867217 is a wasteful number, since it uses less digits than its factorization.

21666867217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101219.

The product of its digits is 2032128, while the sum is 52.

The spelling of 21666867217 in words is "twenty-one billion, six hundred sixty-six million, eight hundred sixty-seven thousand, two hundred seventeen".