21666737279689 has 2 divisors, whose sum is σ = 21666737279690. Its totient is φ = 21666737279688.

The previous prime is 21666737279683. The next prime is 21666737279791. The reversal of 21666737279689 is 98697273766612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13218896208400 + 8447841071289 = 3635780^2 + 2906517^2 .

It is a cyclic number.

It is not a de Polignac number, because 21666737279689 - 2²¹ = 21666735182537 is a prime.

It is not a weakly prime, because it can be changed into another prime (21666737279683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10833368639844 + 10833368639845.

It is an arithmetic number, because the mean of its divisors is an integer number (10833368639845).

Almost surely, 2^{21666737279689} is an apocalyptic number.

It is an amenable number.

21666737279689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666737279689 is an equidigital number, since it uses as much as digits as its factorization.

21666737279689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456649728, while the sum is 79.

The spelling of 21666737279689 in words is "twenty-one trillion, six hundred sixty-six billion, seven hundred thirty-seven million, two hundred seventy-nine thousand, six hundred eighty-nine".