19781693 has 4 divisors (see below), whose sum is σ = 20945340. Its totient is φ = 18618048.

The previous prime is 19781681. The next prime is 19781701. The reversal of 19781693 is 39618791.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14273284 + 5508409 = 3778^2 + 2347^2 .

It is a cyclic number.

It is not a de Polignac number, because 19781693 - 2¹⁰ = 19780669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19781623) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 581798 + ... + 581831.

It is an arithmetic number, because the mean of its divisors is an integer number (5236335).

Almost surely, 2^19781693 is an apocalyptic number.

It is an amenable number.

19781693 is a deficient number, since it is larger than the sum of its proper divisors (1163647).

19781693 is a wasteful number, since it uses less digits than its factorization.

19781693 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1163646.

The product of its digits is 81648, while the sum is 44.

The square root of 19781693 is about 4447.6615203947. The cubic root of 19781693 is about 270.4505189986.

The spelling of 19781693 in words is "nineteen million, seven hundred eighty-one thousand, six hundred ninety-three".