666565541 has 2 divisors, whose sum is σ = 666565542. Its totient is φ = 666565540.

The previous prime is 666565499. The next prime is 666565561. The reversal of 666565541 is 145565666.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 662032900 + 4532641 = 25730^2 + 2129^2 .

It is a cyclic number.

It is not a de Polignac number, because 666565541 - 2⁶ = 666565477 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 666565492 and 666565501.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666565561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333282770 + 333282771.

It is an arithmetic number, because the mean of its divisors is an integer number (333282771).

Almost surely, 2^666565541 is an apocalyptic number.

It is an amenable number.

666565541 is a deficient number, since it is larger than the sum of its proper divisors (1).

666565541 is an equidigital number, since it uses as much as digits as its factorization.

666565541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 648000, while the sum is 44.

The square root of 666565541 is about 25817.9306103336. The cubic root of 666565541 is about 873.5362917993.

The spelling of 666565541 in words is "six hundred sixty-six million, five hundred sixty-five thousand, five hundred forty-one".