666406505 has 8 divisors (see below), whose sum is σ = 801169224. Its totient is φ = 532137600.

The previous prime is 666406493. The next prime is 666406529. The reversal of 666406505 is 505604666.

666406505 is digitally balanced in base 6, 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 86415616 + 579990889 = 9296^2 + 24083^2 .

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

It is not a de Polignac number, because 666406505 - 2⁶ = 666406441 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 120476 + ... + 125885.

It is an arithmetic number, because the mean of its divisors is an integer number (100146153).

Almost surely, 2^666406505 is an apocalyptic number.

It is an amenable number.

666406505 is a deficient number, since it is larger than the sum of its proper divisors (134762719).

666406505 is a wasteful number, since it uses less digits than its factorization.

666406505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246907.

The product of its (nonzero) digits is 129600, while the sum is 38.

The square root of 666406505 is about 25814.8504740973. The cubic root of 666406505 is about 873.4668138764.

The spelling of 666406505 in words is "six hundred sixty-six million, four hundred six thousand, five hundred five".