77640806881 has 27 divisors (see below), whose sum is σ = 86775859443. Its totient is φ = 69415045920.

The previous prime is 77640806849. The next prime is 77640806927. The reversal of 77640806881 is 18860804677.

It is a happy number.

The square root of 77640806881 is 278641.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 44072704225 + 33568102656 = 209935^2 + 183216^2 .

It is not a de Polignac number, because 77640806881 - 2⁵ = 77640806849 is a prime.

It is a super-2 number, since 2×77640806881² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77640804881) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 223748550 + ... + 223748896.

Almost surely, 2^77640806881 is an apocalyptic number.

77640806881 is the 278641-st square number.

77640806881 is the 139321-st centered octagonal number.

It is an amenable number.

77640806881 is a deficient number, since it is larger than the sum of its proper divisors (9135052562).

77640806881 is an frugal number, since it uses more digits than its factorization.

77640806881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 862 (or 431 counting only the distinct ones).

The product of its (nonzero) digits is 3612672, while the sum is 55.

The spelling of 77640806881 in words is "seventy-seven billion, six hundred forty million, eight hundred six thousand, eight hundred eighty-one".