19640 has 16 divisors (see below), whose sum is σ = 44280. Its totient is φ = 7840.

The previous prime is 19609. The next prime is 19661. The reversal of 19640 is 4691.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a plaindrome in base 7.

It is a zygodrome in base 7.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 206 + ... + 285.

2¹⁹⁶⁴⁰ is an apocalyptic number.

19640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

19640 is an abundant number, since it is smaller than the sum of its proper divisors (24640).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22140).

19640 is a wasteful number, since it uses less digits than its factorization.

19640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 502 (or 498 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 19640 is about 140.1427843308. The cubic root of 19640 is about 26.9803240279.

The spelling of 19640 in words is "nineteen thousand, six hundred forty".