11566665421 has 2 divisors, whose sum is σ = 11566665422. Its totient is φ = 11566665420.

The previous prime is 11566665419. The next prime is 11566665427. The reversal of 11566665421 is 12456666511.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11108106025 + 458559396 = 105395^2 + 21414^2 .

It is an emirp because it is prime and its reverse (12456666511) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 11566665421 - 2¹ = 11566665419 is a prime.

It is a super-2 number, since 2×11566665421² (a number of 21 digits) contains 22 as substring.

Together with 11566665419, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11566665427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5783332710 + 5783332711.

It is an arithmetic number, because the mean of its divisors is an integer number (5783332711).

Almost surely, 2^11566665421 is an apocalyptic number.

It is an amenable number.

11566665421 is a deficient number, since it is larger than the sum of its proper divisors (1).

11566665421 is an equidigital number, since it uses as much as digits as its factorization.

11566665421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 259200, while the sum is 43.

The spelling of 11566665421 in words is "eleven billion, five hundred sixty-six million, six hundred sixty-five thousand, four hundred twenty-one".