77178951721 has 9 divisors (see below), whose sum is σ = 77496679191. Its totient is φ = 76862524992.

The previous prime is 77178951673. The next prime is 77178951739. The reversal of 77178951721 is 12715987177.

The square root of 77178951721 is 277811.

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., 31355555625 + 45823396096 = 177075^2 + 214064^2 .

It is not a de Polignac number, because 77178951721 - 2²⁵ = 77145397289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77178951791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 98066890 + ... + 98067676.

Almost surely, 2^77178951721 is an apocalyptic number.

77178951721 is the 277811-st square number.

77178951721 is the 138906-th centered octagonal number.

It is an amenable number.

77178951721 is a deficient number, since it is larger than the sum of its proper divisors (317727470).

77178951721 is an frugal number, since it uses more digits than its factorization.

77178951721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2280 (or 1140 counting only the distinct ones).

The product of its digits is 1728720, while the sum is 55.

The spelling of 77178951721 in words is "seventy-seven billion, one hundred seventy-eight million, nine hundred fifty-one thousand, seven hundred twenty-one".