19816 has 8 divisors (see below), whose sum is σ = 37170. Its totient is φ = 9904.

The previous prime is 19813. The next prime is 19819. The reversal of 19816 is 61891.

It is an interprime number because it is at equal distance from previous prime (19813) and next prime (19819).

It can be written as a sum of positive squares in only one way, i.e., 16900 + 2916 = 130^2 + 54^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (19813) by changing a digit.

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 as a sum of consecutive naturals, namely, 1231 + ... + 1246.

2¹⁹⁸¹⁶ is an apocalyptic number.

It is an amenable number.

19816 is a deficient number, since it is larger than the sum of its proper divisors (17354).

19816 is a wasteful number, since it uses less digits than its factorization.

19816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2483 (or 2479 counting only the distinct ones).

The product of its digits is 432, while the sum is 25.

The square root of 19816 is about 140.7693148381. The cubic root of 19816 is about 27.0606774370.

Subtracting from 19816 its sum of digits (25), we obtain a palindrome (19791).

The spelling of 19816 in words is "nineteen thousand, eight hundred sixteen".