21618691708253 has 2 divisors, whose sum is σ = 21618691708254. Its totient is φ = 21618691708252.

The previous prime is 21618691708247. The next prime is 21618691708387. The reversal of 21618691708253 is 35280719681612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15678099555364 + 5940592152889 = 3959558^2 + 2437333^2 .

It is a cyclic number.

It is not a de Polignac number, because 21618691708253 - 2¹⁰ = 21618691707229 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21618691708192 and 21618691708201.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21618691708853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10809345854126 + 10809345854127.

It is an arithmetic number, because the mean of its divisors is an integer number (10809345854127).

Almost surely, 2^{21618691708253} is an apocalyptic number.

It is an amenable number.

21618691708253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21618691708253 is an equidigital number, since it uses as much as digits as its factorization.

21618691708253 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8709120, while the sum is 59.

The spelling of 21618691708253 in words is "twenty-one trillion, six hundred eighteen billion, six hundred ninety-one million, seven hundred eight thousand, two hundred fifty-three".