78731171820 has 288 divisors, whose sum is σ = 282243526656. Its totient is φ = 17384025600.

The previous prime is 78731171809. The next prime is 78731171903. The reversal of 78731171820 is 2817113787.

It is a happy number.

It is a super-2 number, since 2×78731171820² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 26989002 + ... + 26991918.

Almost surely, 2^78731171820 is an apocalyptic number.

78731171820 is a gapful number since it is divisible by the number (70) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 78731171820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (141121763328).

78731171820 is an abundant number, since it is smaller than the sum of its proper divisors (203512354836).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

78731171820 is a wasteful number, since it uses less digits than its factorization.

78731171820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3661 (or 3656 counting only the distinct ones).

The product of its (nonzero) digits is 131712, while the sum is 45.

The spelling of 78731171820 in words is "seventy-eight billion, seven hundred thirty-one million, one hundred seventy-one thousand, eight hundred twenty".