77491721680 has 40 divisors (see below), whose sum is σ = 180192821832. Its totient is φ = 30992461824.

The previous prime is 77491721641. The next prime is 77491721689. The reversal of 77491721680 is 8612719477.

It can be written as a sum of positive squares in 4 ways, for example, as 26345185344 + 51146536336 = 162312^2 + 226156^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77491721689) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 561292 + ... + 685588.

Almost surely, 2^77491721680 is an apocalyptic number.

It is an amenable number.

77491721680 is an abundant number, since it is smaller than the sum of its proper divisors (102701100152).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

77491721680 is a wasteful number, since it uses less digits than its factorization.

77491721680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132103 (or 132097 counting only the distinct ones).

The product of its (nonzero) digits is 1185408, while the sum is 52.

The spelling of 77491721680 in words is "seventy-seven billion, four hundred ninety-one million, seven hundred twenty-one thousand, six hundred eighty".