19923786781 has 4 divisors (see below), whose sum is σ = 19932307200. Its totient is φ = 19915266364.

The previous prime is 19923786767. The next prime is 19923786787. The reversal of 19923786781 is 18768732991.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18768732991 = 6491 ⋅2891501.

It is a cyclic number.

It is not a de Polignac number, because 19923786781 - 2¹⁵ = 19923754013 is a prime.

It is a super-2 number, since 2×19923786781² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19923786787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4256701 + ... + 4261378.

It is an arithmetic number, because the mean of its divisors is an integer number (4983076800).

Almost surely, 2^19923786781 is an apocalyptic number.

It is an amenable number.

19923786781 is a deficient number, since it is larger than the sum of its proper divisors (8520419).

19923786781 is an equidigital number, since it uses as much as digits as its factorization.

19923786781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8520418.

The product of its digits is 9144576, while the sum is 61.

The spelling of 19923786781 in words is "nineteen billion, nine hundred twenty-three million, seven hundred eighty-six thousand, seven hundred eighty-one".