1665990 has 48 divisors (see below), whose sum is σ = 4397328. Its totient is φ = 437568.

The previous prime is 1665973. The next prime is 1665997. The reversal of 1665990 is 995661.

1665990 is a `hidden beast` number, since 1 + 66 + 599 + 0 = 666.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665997) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9544 + ... + 9716.

It is an arithmetic number, because the mean of its divisors is an integer number (91611).

2^1665990 is an apocalyptic number.

1665990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1665990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2198664).

1665990 is an abundant number, since it is smaller than the sum of its proper divisors (2731338).

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

1665990 is a wasteful number, since it uses less digits than its factorization.

1665990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293 (or 290 counting only the distinct ones).

The product of its (nonzero) digits is 14580, while the sum is 36.

The square root of 1665990 is about 1290.7323502570. The cubic root of 1665990 is about 118.5470624368.

The spelling of 1665990 in words is "one million, six hundred sixty-five thousand, nine hundred ninety".