1666656505 has 4 divisors (see below), whose sum is σ = 1999987812. Its totient is φ = 1333325200.

The previous prime is 1666656491. The next prime is 1666656529. The reversal of 1666656505 is 5056566661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 633226896 + 1033429609 = 25164^2 + 32147^2 .

It is not a de Polignac number, because 1666656505 - 2⁷ = 1666656377 is a prime.

It is a Duffinian number.

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 3 ways as a sum of consecutive naturals, for example, 166665646 + ... + 166665655.

It is an arithmetic number, because the mean of its divisors is an integer number (499996953).

Almost surely, 2^1666656505 is an apocalyptic number.

It is an amenable number.

1666656505 is a deficient number, since it is larger than the sum of its proper divisors (333331307).

1666656505 is an equidigital number, since it uses as much as digits as its factorization.

1666656505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333331306.

The product of its (nonzero) digits is 972000, while the sum is 46.

The square root of 1666656505 is about 40824.7045917053. The cubic root of 1666656505 is about 1185.6286918942.

The spelling of 1666656505 in words is "one billion, six hundred sixty-six million, six hundred fifty-six thousand, five hundred five".