16640 has 36 divisors (see below), whose sum is σ = 42924. Its totient is φ = 6144.

The previous prime is 16633. The next prime is 16649. The reversal of 16640 is 4661.

It is a Cunningham number, because it is equal to 129²-1.

It can be written as a sum of positive squares in 2 ways, for example, as 4096 + 12544 = 64^2 + 112^2 .

It is a plaindrome in base 11.

It is a nialpdrome in base 13 and base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (2) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1274 + ... + 1286.

2¹⁶⁶⁴⁰ is an apocalyptic number.

16640 is a gapful number since it is divisible by the number (10) 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 16640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21462).

16640 is an abundant number, since it is smaller than the sum of its proper divisors (26284).

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

16640 is an equidigital number, since it uses as much as digits as its factorization.

16640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34 (or 20 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 16640 is about 128.9961239728. The cubic root of 16640 is about 25.5300171954.

It can be divided in two parts, 16 and 640, that added together give a palindrome (656).

The spelling of 16640 in words is "sixteen thousand, six hundred forty".