19718707681 has 2 divisors, whose sum is σ = 19718707682. Its totient is φ = 19718707680.

The previous prime is 19718707669. The next prime is 19718707703. The reversal of 19718707681 is 18670781791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12733091281 + 6985616400 = 112841^2 + 83580^2 .

It is an emirp because it is prime and its reverse (18670781791) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19718707681 is a prime.

It is a super-2 number, since 2×19718707681² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (19718707601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9859353840 + 9859353841.

It is an arithmetic number, because the mean of its divisors is an integer number (9859353841).

Almost surely, 2^19718707681 is an apocalyptic number.

It is an amenable number.

19718707681 is a deficient number, since it is larger than the sum of its proper divisors (1).

19718707681 is an equidigital number, since it uses as much as digits as its factorization.

19718707681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1185408, while the sum is 55.

The spelling of 19718707681 in words is "nineteen billion, seven hundred eighteen million, seven hundred seven thousand, six hundred eighty-one".