21618691708247 has 2 divisors, whose sum is σ = 21618691708248. Its totient is φ = 21618691708246.

The previous prime is 21618691708241. The next prime is 21618691708253. The reversal of 21618691708247 is 74280719681612.

It is a balanced prime because it is at equal distance from previous prime (21618691708241) and next prime (21618691708253).

It is a cyclic number.

It is not a de Polignac number, because 21618691708247 - 2⁴⁰ = 20519180080471 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21618691708247.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21618691708241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10809345854123 + 10809345854124.

It is an arithmetic number, because the mean of its divisors is an integer number (10809345854124).

Almost surely, 2^{21618691708247} is an apocalyptic number.

21618691708247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21618691708247 is an equidigital number, since it uses as much as digits as its factorization.

21618691708247 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16257024, while the sum is 62.

The spelling of 21618691708247 in words is "twenty-one trillion, six hundred eighteen billion, six hundred ninety-one million, seven hundred eight thousand, two hundred forty-seven".