77749561 has 4 divisors (see below), whose sum is σ = 77767312. Its totient is φ = 77731812.

The previous prime is 77749549. The next prime is 77749579. The reversal of 77749561 is 16594777.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 16594777 = 53 ⋅313109.

It is a cyclic number.

It is not a de Polignac number, because 77749561 - 2¹¹ = 77747513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77749961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2926 + ... + 12808.

It is an arithmetic number, because the mean of its divisors is an integer number (19441828).

Almost surely, 2^77749561 is an apocalyptic number.

It is an amenable number.

77749561 is a deficient number, since it is larger than the sum of its proper divisors (17751).

77749561 is an equidigital number, since it uses as much as digits as its factorization.

77749561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17750.

The product of its digits is 370440, while the sum is 46.

The square root of 77749561 is about 8817.5711508329. The cubic root of 77749561 is about 426.8080956793.

The spelling of 77749561 in words is "seventy-seven million, seven hundred forty-nine thousand, five hundred sixty-one".