77818681 has 4 divisors (see below), whose sum is σ = 79287012. Its totient is φ = 76350352.

The previous prime is 77818679. The next prime is 77818721. The reversal of 77818681 is 18681877.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18681877 = 911 ⋅20507.

It can be written as a sum of positive squares in 2 ways, for example, as 43771456 + 34047225 = 6616^2 + 5835^2 .

It is a cyclic number.

It is not a de Polignac number, because 77818681 - 2¹ = 77818679 is a prime.

It is a super-2 number, since 2×77818681² = 12111494225159522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77818621) 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, 734086 + ... + 734191.

It is an arithmetic number, because the mean of its divisors is an integer number (19821753).

Almost surely, 2^77818681 is an apocalyptic number.

It is an amenable number.

77818681 is a deficient number, since it is larger than the sum of its proper divisors (1468331).

77818681 is a wasteful number, since it uses less digits than its factorization.

77818681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1468330.

The product of its digits is 150528, while the sum is 46.

The square root of 77818681 is about 8821.4897267978. The cubic root of 77818681 is about 426.9345368549.

The spelling of 77818681 in words is "seventy-seven million, eight hundred eighteen thousand, six hundred eighty-one".