77661 has 6 divisors (see below), whose sum is σ = 112190. Its totient is φ = 51768.

The previous prime is 77659. The next prime is 77681. The reversal of 77661 is 16677.

It can be written as a sum of positive squares in only one way, i.e., 72900 + 4761 = 270^2 + 69^2 .

It is not a de Polignac number, because 77661 - 2¹ = 77659 is a prime.

It is an Ulam number.

It is a Duffinian number.

77661 is a lucky number.

It is a nialpdrome in base 10.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 77661.

It is not an unprimeable number, because it can be changed into a prime (77611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4306 + ... + 4323.

2⁷⁷⁶⁶¹ is an apocalyptic number.

It is an amenable number.

77661 is a deficient number, since it is larger than the sum of its proper divisors (34529).

77661 is a wasteful number, since it uses less digits than its factorization.

77661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8635 (or 8632 counting only the distinct ones).

The product of its digits is 1764, while the sum is 27.

The square root of 77661 is about 278.6772326546. The cubic root of 77661 is about 42.6645981528.

The spelling of 77661 in words is "seventy-seven thousand, six hundred sixty-one".