1661665566666 has 16 divisors (see below), whose sum is σ = 3798092723904. Its totient is φ = 474761590464.

The previous prime is 1661665566641. The next prime is 1661665566677. The reversal of 1661665566666 is 6666655661661.

It is a happy number.

It is a super-2 number, since 2×1661665566666² (a number of 25 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1661665566597 and 1661665566606.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19781732895 + ... + 19781732978.

It is an arithmetic number, because the mean of its divisors is an integer number (237380795244).

Almost surely, 2^{1661665566666} is an apocalyptic number.

1661665566666 is an abundant number, since it is smaller than the sum of its proper divisors (2136427157238).

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

1661665566666 is a wasteful number, since it uses less digits than its factorization.

1661665566666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39563465885.

The product of its digits is 251942400, while the sum is 66.

The spelling of 1661665566666 in words is "one trillion, six hundred sixty-one billion, six hundred sixty-five million, five hundred sixty-six thousand, six hundred sixty-six".