77521758661 has 4 divisors (see below), whose sum is σ = 78087611052. Its totient is φ = 76955906272.

The previous prime is 77521758653. The next prime is 77521758673. The reversal of 77521758661 is 16685712577.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 47739628036 + 29782130625 = 218494^2 + 172575^2 .

It is a cyclic number.

It is not a de Polignac number, because 77521758661 - 2³ = 77521758653 is a prime.

It is a super-7 number, since 7×77521758661⁷ (a number of 78 digits) contains 7777777 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77521758961) 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, 282925990 + ... + 282926263.

It is an arithmetic number, because the mean of its divisors is an integer number (19521902763).

Almost surely, 2^77521758661 is an apocalyptic number.

It is an amenable number.

77521758661 is a deficient number, since it is larger than the sum of its proper divisors (565852391).

77521758661 is a wasteful number, since it uses less digits than its factorization.

77521758661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 565852390.

The product of its digits is 4939200, while the sum is 55.

The spelling of 77521758661 in words is "seventy-seven billion, five hundred twenty-one million, seven hundred fifty-eight thousand, six hundred sixty-one".