77678561 has 2 divisors, whose sum is σ = 77678562. Its totient is φ = 77678560.

The previous prime is 77678551. The next prime is 77678563. The reversal of 77678561 is 16587677.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 76457536 + 1221025 = 8744^2 + 1105^2 .

It is an emirp because it is prime and its reverse (16587677) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77678561 is a prime.

It is a Sophie Germain prime.

Together with 77678563, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (77678563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38839280 + 38839281.

It is an arithmetic number, because the mean of its divisors is an integer number (38839281).

Almost surely, 2^77678561 is an apocalyptic number.

It is an amenable number.

77678561 is a deficient number, since it is larger than the sum of its proper divisors (1).

77678561 is an equidigital number, since it uses as much as digits as its factorization.

77678561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 493920, while the sum is 47.

The square root of 77678561 is about 8813.5441792732. The cubic root of 77678561 is about 426.6781373734.

The spelling of 77678561 in words is "seventy-seven million, six hundred seventy-eight thousand, five hundred sixty-one".