778215011681 has 4 divisors (see below), whose sum is σ = 779392342164. Its totient is φ = 777037681200.

The previous prime is 778215011677. The next prime is 778215011771. The reversal of 778215011681 is 186110512877.

778215011681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 186110512877 = 293729 ⋅633613.

It can be written as a sum of positive squares in 2 ways, for example, as 586472614225 + 191742397456 = 765815^2 + 437884^2 .

It is a cyclic number.

It is not a de Polignac number, because 778215011681 - 2² = 778215011677 is a prime.

It is a super-2 number, since 2×778215011681² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (778215071681) 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, 588664250 + ... + 588665571.

It is an arithmetic number, because the mean of its divisors is an integer number (194848085541).

Almost surely, 2^778215011681 is an apocalyptic number.

It is an amenable number.

778215011681 is a deficient number, since it is larger than the sum of its proper divisors (1177330483).

778215011681 is a wasteful number, since it uses less digits than its factorization.

778215011681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1177330482.

The product of its (nonzero) digits is 188160, while the sum is 47.

The spelling of 778215011681 in words is "seven hundred seventy-eight billion, two hundred fifteen million, eleven thousand, six hundred eighty-one".