1666820018197 has 16 divisors (see below), whose sum is σ = 1734971879664. Its totient is φ = 1599998400000.

The previous prime is 1666820018177. The next prime is 1666820018219. The reversal of 1666820018197 is 7918100286661.

It can be written as a sum of positive squares in 8 ways, for example, as 725970457521 + 940849560676 = 852039^2 + 969974^2 .

It is a de Polignac number, because none of the positive numbers 2^k-1666820018197 is a prime.

It is a super-2 number, since 2×1666820018197² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666820018107) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 256447 + ... + 1843747.

It is an arithmetic number, because the mean of its divisors is an integer number (108435742479).

Almost surely, 2^{1666820018197} is an apocalyptic number.

It is an amenable number.

1666820018197 is a deficient number, since it is larger than the sum of its proper divisors (68151861467).

1666820018197 is a wasteful number, since it uses less digits than its factorization.

1666820018197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1587720.

The product of its (nonzero) digits is 1741824, while the sum is 55.

The spelling of 1666820018197 in words is "one trillion, six hundred sixty-six billion, eight hundred twenty million, eighteen thousand, one hundred ninety-seven".