15978438409 has 4 divisors (see below), whose sum is σ = 15978822804. Its totient is φ = 15978054016.

The previous prime is 15978438403. The next prime is 15978438439. The reversal of 15978438409 is 90483487951.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90483487951 = 937 ⋅96567223.

It can be written as a sum of positive squares in 2 ways, for example, as 3784095225 + 12194343184 = 61515^2 + 110428^2 .

It is a cyclic number.

It is not a de Polignac number, because 15978438409 - 2¹³ = 15978430217 is a prime.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15978438403) 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, 121072 + ... + 215905.

It is an arithmetic number, because the mean of its divisors is an integer number (3994705701).

Almost surely, 2^15978438409 is an apocalyptic number.

It is an amenable number.

15978438409 is a deficient number, since it is larger than the sum of its proper divisors (384395).

15978438409 is an equidigital number, since it uses as much as digits as its factorization.

15978438409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384394.

The product of its (nonzero) digits is 8709120, while the sum is 58.

The spelling of 15978438409 in words is "fifteen billion, nine hundred seventy-eight million, four hundred thirty-eight thousand, four hundred nine".