1643688 has 48 divisors (see below), whose sum is σ = 4579380. Its totient is φ = 532224.

The previous prime is 1643687. The next prime is 1643693. The reversal of 1643688 is 8863461.

It is a happy number.

1643688 is a `hidden beast` number, since 1 + 643 + 6 + 8 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1633284 + 10404 = 1278^2 + 102^2 .

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).

It is a nude number because it is divisible by every one of its digits.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (1643683) 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, 2356 + ... + 2972.

2^1643688 is an apocalyptic number.

1643688 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 1643688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2289690).

1643688 is an abundant number, since it is smaller than the sum of its proper divisors (2935692).

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

1643688 is a wasteful number, since it uses less digits than its factorization.

1643688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 666 (or 659 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 1643688 is about 1282.0639609629. The cubic root of 1643688 is about 118.0157022100.

The spelling of 1643688 in words is "one million, six hundred forty-three thousand, six hundred eighty-eight".