1666555605 has 48 divisors (see below), whose sum is σ = 3393726336. Its totient is φ = 745868160.

The previous prime is 1666555573. The next prime is 1666555621. The reversal of 1666555605 is 5065556661.

It is not a de Polignac number, because 1666555605 - 2⁵ = 1666555573 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 123057 + ... + 135926.

It is an arithmetic number, because the mean of its divisors is an integer number (70702632).

Almost surely, 2^1666555605 is an apocalyptic number.

1666555605 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1666555605 is an abundant number, since it is smaller than the sum of its proper divisors (1727170731).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1666555605 is a wasteful number, since it uses less digits than its factorization.

1666555605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259018 (or 259015 counting only the distinct ones).

The product of its (nonzero) digits is 810000, while the sum is 45.

The square root of 1666555605 is about 40823.4688016587. The cubic root of 1666555605 is about 1185.6047652785.

The spelling of 1666555605 in words is "one billion, six hundred sixty-six million, five hundred fifty-five thousand, six hundred five".