77561755729920 has 2592 divisors, whose sum is σ = 352667277720576. Its totient is φ = 15577015910400.

The previous prime is 77561755729907. The next prime is 77561755729961. The reversal of 77561755729920 is 2992755716577.

It is a happy number.

77561755729920 is a `hidden beast` number, since 7 + 7 + 5 + 61 + 7 + 557 + 2 + 9 + 9 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 98553691767 + ... + 98553692553.

It is an arithmetic number, because the mean of its divisors is an integer number (136059906528).

Almost surely, 2^{77561755729920} is an apocalyptic number.

77561755729920 is a gapful number since it is divisible by the number (70) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 77561755729920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (176333638860288).

77561755729920 is an abundant number, since it is smaller than the sum of its proper divisors (275105521990656).

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

77561755729920 is a wasteful number, since it uses less digits than its factorization.

77561755729920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 888 (or 846 counting only the distinct ones).

The product of its (nonzero) digits is 583443000, while the sum is 72.

The spelling of 77561755729920 in words is "seventy-seven trillion, five hundred sixty-one billion, seven hundred fifty-five million, seven hundred twenty-nine thousand, nine hundred twenty".