1666890 has 24 divisors (see below), whose sum is σ = 4334148. Its totient is φ = 444480.

The previous prime is 1666871. The next prime is 1666897. The reversal of 1666890 is 986661.

It can be written as a sum of positive squares in 2 ways, for example, as 1535121 + 131769 = 1239^2 + 363^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666897) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9171 + ... + 9350.

2^1666890 is an apocalyptic number.

1666890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1666890 is an abundant number, since it is smaller than the sum of its proper divisors (2667258).

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

1666890 is a wasteful number, since it uses less digits than its factorization.

1666890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18534 (or 18531 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 1666890 is about 1291.0809424664. The cubic root of 1666890 is about 118.5684057321.

It can be divided in two parts, 1666 and 890, that added together give a triangular number (2556 = T₇₁).

The spelling of 1666890 in words is "one million, six hundred sixty-six thousand, eight hundred ninety".