1666881 has 12 divisors (see below), whose sum is σ = 2435940. Its totient is φ = 1098240.

The previous prime is 1666871. The next prime is 1666897. The reversal of 1666881 is 1886661.

It can be written as a sum of positive squares in 2 ways, for example, as 467856 + 1199025 = 684^2 + 1095^2 .

It is not a de Polignac number, because 1666881 - 2¹¹ = 1664833 is a prime.

It is a super-3 number, since 3×1666881³ = 13894247911333427523, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (1666811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 240 + ... + 1841.

It is an arithmetic number, because the mean of its divisors is an integer number (202995).

2^1666881 is an apocalyptic number.

It is an amenable number.

1666881 is a deficient number, since it is larger than the sum of its proper divisors (769059).

1666881 is a wasteful number, since it uses less digits than its factorization.

1666881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2176 (or 2173 counting only the distinct ones).

The product of its digits is 13824, while the sum is 36.

The square root of 1666881 is about 1291.0774570102. The cubic root of 1666881 is about 118.5681923371.

The spelling of 1666881 in words is "one million, six hundred sixty-six thousand, eight hundred eighty-one".