77720045521 has 2 divisors, whose sum is σ = 77720045522. Its totient is φ = 77720045520.

The previous prime is 77720045497. The next prime is 77720045537. The reversal of 77720045521 is 12554002777.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62145005521 + 15575040000 = 249289^2 + 124800^2 .

It is an emirp because it is prime and its reverse (12554002777) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77720045521 - 2⁵ = 77720045489 is a prime.

It is a super-3 number, since 3×77720045521³ (a number of 34 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (77720045021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38860022760 + 38860022761.

It is an arithmetic number, because the mean of its divisors is an integer number (38860022761).

Almost surely, 2^77720045521 is an apocalyptic number.

It is an amenable number.

77720045521 is a deficient number, since it is larger than the sum of its proper divisors (1).

77720045521 is an equidigital number, since it uses as much as digits as its factorization.

77720045521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 137200, while the sum is 40.

The spelling of 77720045521 in words is "seventy-seven billion, seven hundred twenty million, forty-five thousand, five hundred twenty-one".