6566665421 has 2 divisors, whose sum is σ = 6566665422. Its totient is φ = 6566665420.

The previous prime is 6566665409. The next prime is 6566665423. The reversal of 6566665421 is 1245666656.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5805678025 + 760987396 = 76195^2 + 27586^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6566665421 is a prime.

Together with 6566665423, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6566665423) 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, 3283332710 + 3283332711.

It is an arithmetic number, because the mean of its divisors is an integer number (3283332711).

Almost surely, 2^6566665421 is an apocalyptic number.

It is an amenable number.

6566665421 is a deficient number, since it is larger than the sum of its proper divisors (1).

6566665421 is an equidigital number, since it uses as much as digits as its factorization.

6566665421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1555200, while the sum is 47.

The square root of 6566665421 is about 81034.9641883058. The cubic root of 6566665421 is about 1872.6141312000.

The spelling of 6566665421 in words is "six billion, five hundred sixty-six million, six hundred sixty-five thousand, four hundred twenty-one".