6566611621 has 2 divisors, whose sum is σ = 6566611622. Its totient is φ = 6566611620.

The previous prime is 6566611613. The next prime is 6566611663. The reversal of 6566611621 is 1261166656.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5028795396 + 1537816225 = 70914^2 + 39215^2 .

It is a cyclic number.

It is not a de Polignac number, because 6566611621 - 2³ = 6566611613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6566611321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3283305810 + 3283305811.

It is an arithmetic number, because the mean of its divisors is an integer number (3283305811).

Almost surely, 2^6566611621 is an apocalyptic number.

It is an amenable number.

6566611621 is a deficient number, since it is larger than the sum of its proper divisors (1).

6566611621 is an equidigital number, since it uses as much as digits as its factorization.

6566611621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 77760, while the sum is 40.

The square root of 6566611621 is about 81034.6322321512. The cubic root of 6566611621 is about 1872.6090171424.

The spelling of 6566611621 in words is "six billion, five hundred sixty-six million, six hundred eleven thousand, six hundred twenty-one".