1778318661666 has 16 divisors (see below), whose sum is σ = 3765851283744. Its totient is φ = 557903893824.

The previous prime is 1778318661607. The next prime is 1778318661667. The reversal of 1778318661666 is 6661668138771.

It is a junction number, because it is equal to n+sod(n) for n = 1778318661597 and 1778318661606.

It is not an unprimeable number, because it can be changed into a prime (1778318661667) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8717248240 + ... + 8717248443.

It is an arithmetic number, because the mean of its divisors is an integer number (235365705234).

Almost surely, 2^{1778318661666} is an apocalyptic number.

1778318661666 is an abundant number, since it is smaller than the sum of its proper divisors (1987532622078).

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

1778318661666 is a wasteful number, since it uses less digits than its factorization.

1778318661666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17434496705.

The product of its digits is 73156608, while the sum is 66.

The spelling of 1778318661666 in words is "one trillion, seven hundred seventy-eight billion, three hundred eighteen million, six hundred sixty-one thousand, six hundred sixty-six".