77615561 has 2 divisors, whose sum is σ = 77615562. Its totient is φ = 77615560.

The previous prime is 77615543. The next prime is 77615563. The reversal of 77615561 is 16551677.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77440000 + 175561 = 8800^2 + 419^2 .

It is an emirp because it is prime and its reverse (16551677) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77615561 - 2⁶ = 77615497 is a prime.

Together with 77615563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (77615563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38807780 + 38807781.

It is an arithmetic number, because the mean of its divisors is an integer number (38807781).

Almost surely, 2^77615561 is an apocalyptic number.

It is an amenable number.

77615561 is a deficient number, since it is larger than the sum of its proper divisors (1).

77615561 is an equidigital number, since it uses as much as digits as its factorization.

77615561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 44100, while the sum is 38.

The square root of 77615561 is about 8809.9694097085. The cubic root of 77615561 is about 426.5627559320.

The spelling of 77615561 in words is "seventy-seven million, six hundred fifteen thousand, five hundred sixty-one".