666262561 has 2 divisors, whose sum is σ = 666262562. Its totient is φ = 666262560.

The previous prime is 666262543. The next prime is 666262567. The reversal of 666262561 is 165262666.

666262561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 492840000 + 173422561 = 22200^2 + 13169^2 .

It is a cyclic number.

It is not a de Polignac number, because 666262561 - 2⁵ = 666262529 is a prime.

It is not a weakly prime, because it can be changed into another prime (666262567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333131280 + 333131281.

It is an arithmetic number, because the mean of its divisors is an integer number (333131281).

Almost surely, 2^666262561 is an apocalyptic number.

It is an amenable number.

666262561 is a deficient number, since it is larger than the sum of its proper divisors (1).

666262561 is an equidigital number, since it uses as much as digits as its factorization.

666262561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 155520, while the sum is 40.

The square root of 666262561 is about 25812.0623159018. The cubic root of 666262561 is about 873.4039196520.

The spelling of 666262561 in words is "six hundred sixty-six million, two hundred sixty-two thousand, five hundred sixty-one".