1663668 has 36 divisors (see below), whose sum is σ = 4322500. Its totient is φ = 539136.

The previous prime is 1663619. The next prime is 1663681. The reversal of 1663668 is 8663661.

1663668 is a `hidden beast` number, since 16 + 636 + 6 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1127844 + 535824 = 1062^2 + 732^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

Its product of digits (31104) is a multiple of the sum of its prime factors (1296).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 708 + ... + 1956.

2^1663668 is an apocalyptic number.

1663668 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1663668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2161250).

1663668 is an abundant number, since it is smaller than the sum of its proper divisors (2658832).

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

1663668 is a wasteful number, since it uses less digits than its factorization.

1663668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1296 (or 1291 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 1663668 is about 1289.8325472712. The cubic root of 1663668 is about 118.4919612129.

The spelling of 1663668 in words is "one million, six hundred sixty-three thousand, six hundred sixty-eight".