8131978209 has 4 divisors (see below), whose sum is σ = 10842637616. Its totient is φ = 5421318804.

The previous prime is 8131978199. The next prime is 8131978213. The reversal of 8131978209 is 9028791318.

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.

It is not a de Polignac number, because 8131978209 - 2⁷ = 8131978081 is a prime.

It is a super-2 number, since 2×8131978209² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8131971209) 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, 1355329699 + ... + 1355329704.

It is an arithmetic number, because the mean of its divisors is an integer number (2710659404).

Almost surely, 2^8131978209 is an apocalyptic number.

It is an amenable number.

8131978209 is a deficient number, since it is larger than the sum of its proper divisors (2710659407).

8131978209 is a wasteful number, since it uses less digits than its factorization.

8131978209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2710659406.

The product of its (nonzero) digits is 217728, while the sum is 48.

The square root of 8131978209 is about 90177.4817179988. The cubic root of 8131978209 is about 2010.9382523419.

The spelling of 8131978209 in words is "eight billion, one hundred thirty-one million, nine hundred seventy-eight thousand, two hundred nine".