1666688555 has 32 divisors (see below), whose sum is σ = 2319819264. Its totient is φ = 1125916416.

The previous prime is 1666688549. The next prime is 1666688561. The reversal of 1666688555 is 5558866661.

It is an interprime number because it is at equal distance from previous prime (1666688549) and next prime (1666688561).

It is a cyclic number.

It is not a de Polignac number, because 1666688555 - 2²⁴ = 1649911339 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1666688555.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1518767 + ... + 1519863.

It is an arithmetic number, because the mean of its divisors is an integer number (72494352).

Almost surely, 2^1666688555 is an apocalyptic number.

1666688555 is a deficient number, since it is larger than the sum of its proper divisors (653130709).

1666688555 is a wasteful number, since it uses less digits than its factorization.

1666688555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1715.

The product of its digits is 10368000, while the sum is 56.

The square root of 1666688555 is about 40825.0971217461. The cubic root of 1666688555 is about 1185.6362917717.

The spelling of 1666688555 in words is "one billion, six hundred sixty-six million, six hundred eighty-eight thousand, five hundred fifty-five".