77780561 has 2 divisors, whose sum is σ = 77780562. Its totient is φ = 77780560.

The previous prime is 77780557. The next prime is 77780597. The reversal of 77780561 is 16508777.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76667536 + 1113025 = 8756^2 + 1055^2 .

It is a cyclic number.

It is not a de Polignac number, because 77780561 - 2² = 77780557 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (77788561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38890280 + 38890281.

It is an arithmetic number, because the mean of its divisors is an integer number (38890281).

Almost surely, 2^77780561 is an apocalyptic number.

It is an amenable number.

77780561 is a deficient number, since it is larger than the sum of its proper divisors (1).

77780561 is an equidigital number, since it uses as much as digits as its factorization.

77780561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 82320, while the sum is 41.

The square root of 77780561 is about 8819.3288293384. The cubic root of 77780561 is about 426.8648132252.

The spelling of 77780561 in words is "seventy-seven million, seven hundred eighty thousand, five hundred sixty-one".