1666112120721 has 20 divisors (see below), whose sum is σ = 2502634298164. Its totient is φ = 1104604711200.

The previous prime is 1666112120707. The next prime is 1666112120731. The reversal of 1666112120721 is 1270212116661.

It can be written as a sum of positive squares in 2 ways, for example, as 847340501121 + 818771619600 = 920511^2 + 904860^2 .

It is not a de Polignac number, because 1666112120721 - 2¹¹ = 1666112118673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666112120731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 56806570 + ... + 56835891.

Almost surely, 2^{1666112120721} is an apocalyptic number.

It is an amenable number.

1666112120721 is a deficient number, since it is larger than the sum of its proper divisors (836522177443).

1666112120721 is a wasteful number, since it uses less digits than its factorization.

1666112120721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113642654 (or 113642645 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The spelling of 1666112120721 in words is "one trillion, six hundred sixty-six billion, one hundred twelve million, one hundred twenty thousand, seven hundred twenty-one".