666455561 has 8 divisors (see below), whose sum is σ = 677799624. Its totient is φ = 655125120.

The previous prime is 666455519. The next prime is 666455593. The reversal of 666455561 is 165554666.

It is a happy number.

666455561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 1795600 + 664659961 = 1340^2 + 25781^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 666455561 - 2⁶ = 666455497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666452561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 162245 + ... + 166301.

It is an arithmetic number, because the mean of its divisors is an integer number (84724953).

Almost surely, 2^666455561 is an apocalyptic number.

666455561 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

666455561 is a deficient number, since it is larger than the sum of its proper divisors (11344063).

666455561 is a wasteful number, since it uses less digits than its factorization.

666455561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6811.

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

The square root of 666455561 is about 25815.8006073800. The cubic root of 666455561 is about 873.4882461085.

The spelling of 666455561 in words is "six hundred sixty-six million, four hundred fifty-five thousand, five hundred sixty-one".