21666844794139 has 2 divisors, whose sum is σ = 21666844794140. Its totient is φ = 21666844794138.

The previous prime is 21666844794131. The next prime is 21666844794173. The reversal of 21666844794139 is 93149744866612.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21666844794139 - 2³ = 21666844794131 is a prime.

It is not a weakly prime, because it can be changed into another prime (21666844794131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10833422397069 + 10833422397070.

It is an arithmetic number, because the mean of its divisors is an integer number (10833422397070).

Almost surely, 2^{21666844794139} is an apocalyptic number.

21666844794139 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666844794139 is an equidigital number, since it uses as much as digits as its factorization.

21666844794139 is an evil number, because the sum of its binary digits is even.

The product of its digits is 376233984, while the sum is 70.

The spelling of 21666844794139 in words is "twenty-one trillion, six hundred sixty-six billion, eight hundred forty-four million, seven hundred ninety-four thousand, one hundred thirty-nine".