19439681 has 4 divisors (see below), whose sum is σ = 19706052. Its totient is φ = 19173312.

The previous prime is 19439639. The next prime is 19439683. The reversal of 19439681 is 18693491.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18693491 = 2677 ⋅6983.

It can be written as a sum of positive squares in 2 ways, for example, as 11122225 + 8317456 = 3335^2 + 2884^2 .

It is a cyclic number.

It is not a de Polignac number, because 19439681 - 2¹⁴ = 19423297 is a prime.

It is a super-2 number, since 2×19439681² = 755802394763522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19439683) 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 in 3 ways as a sum of consecutive naturals, for example, 133076 + ... + 133221.

It is an arithmetic number, because the mean of its divisors is an integer number (4926513).

Almost surely, 2^19439681 is an apocalyptic number.

It is an amenable number.

19439681 is a deficient number, since it is larger than the sum of its proper divisors (266371).

19439681 is an equidigital number, since it uses as much as digits as its factorization.

19439681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266370.

The product of its digits is 46656, while the sum is 41.

The square root of 19439681 is about 4409.0453615267. The cubic root of 19439681 is about 268.8828140363.

The spelling of 19439681 in words is "nineteen million, four hundred thirty-nine thousand, six hundred eighty-one".