77842 has 4 divisors (see below), whose sum is σ = 116766. Its totient is φ = 38920.

The previous prime is 77839. The next prime is 77849. The reversal of 77842 is 24877.

It is a Cunningham number, because it is equal to 279²+1.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 77841 + 1 = 279^2 + 1^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 77842.

It is not an unprimeable number, because it can be changed into a prime (77849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19459 + ... + 19462.

2⁷⁷⁸⁴² is an apocalyptic number.

77842 is a deficient number, since it is larger than the sum of its proper divisors (38924).

77842 is a wasteful number, since it uses less digits than its factorization.

77842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38923.

The product of its digits is 3136, while the sum is 28.

The square root of 77842 is about 279.0017921089. The cubic root of 77842 is about 42.6977177397.

It can be divided in two parts, 778 and 42, that added together give a triangular number (820 = T₄₀).

The spelling of 77842 in words is "seventy-seven thousand, eight hundred forty-two".