19869439681 has 27 divisors (see below), whose sum is σ = 25044319881. Its totient is φ = 15710726304.

The previous prime is 19869439679. The next prime is 19869439691. The reversal of 19869439681 is 18693496891.

The square root of 19869439681 is 140959.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 5521233025 + 14348206656 = 74305^2 + 119784^2 .

It is not a de Polignac number, because 19869439681 - 2¹ = 19869439679 is a prime.

It is a super-2 number, since 2×19869439681² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (19869439621) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 12826495 + ... + 12828043.

It is an arithmetic number, because the mean of its divisors is an integer number (927567403).

Almost surely, 2^19869439681 is an apocalyptic number.

19869439681 is the 140959-th square number.

19869439681 is the 70480-th centered octagonal number.

It is an amenable number.

19869439681 is a deficient number, since it is larger than the sum of its proper divisors (5174880200).

19869439681 is an frugal number, since it uses more digits than its factorization.

19869439681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3138 (or 1569 counting only the distinct ones).

The product of its digits is 20155392, while the sum is 64.

Multiplying 19869439681 by its sum of digits (64), we get a square (1271644139584 = 1127672²).

The spelling of 19869439681 in words is "nineteen billion, eight hundred sixty-nine million, four hundred thirty-nine thousand, six hundred eighty-one".