78312815921 has 12 divisors (see below), whose sum is σ = 80371561116. Its totient is φ = 76305578880.

The previous prime is 78312815887. The next prime is 78312815923. The reversal of 78312815921 is 12951821387.

It can be written as a sum of positive squares in 6 ways, for example, as 47375875600 + 30936940321 = 217660^2 + 175889^2 .

It is not a de Polignac number, because 78312815921 - 2⁶ = 78312815857 is a prime.

It is a super-3 number, since 3×78312815921³ (a number of 34 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78312815923) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1310531 + ... + 1368983.

It is an arithmetic number, because the mean of its divisors is an integer number (6697630093).

Almost surely, 2^78312815921 is an apocalyptic number.

It is an amenable number.

78312815921 is a deficient number, since it is larger than the sum of its proper divisors (2058745195).

78312815921 is an equidigital number, since it uses as much as digits as its factorization.

78312815921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59332 (or 59291 counting only the distinct ones).

The product of its digits is 241920, while the sum is 47.

The spelling of 78312815921 in words is "seventy-eight billion, three hundred twelve million, eight hundred fifteen thousand, nine hundred twenty-one".