84781 has 4 divisors (see below), whose sum is σ = 85500. Its totient is φ = 84064.

The previous prime is 84761. The next prime is 84787. The reversal of 84781 is 18748.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 11881 + 72900 = 109^2 + 270^2 .

It is a cyclic number.

It is not a de Polignac number, because 84781 - 2⁷ = 84653 is a prime.

It is a super-2 number, since 2×84781² = 14375635922, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

84781 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (84787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136 + ... + 433.

It is an arithmetic number, because the mean of its divisors is an integer number (21375).

2⁸⁴⁷⁸¹ is an apocalyptic number.

It is an amenable number.

84781 is a deficient number, since it is larger than the sum of its proper divisors (719).

84781 is a wasteful number, since it uses less digits than its factorization.

84781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 718.

The product of its digits is 1792, while the sum is 28.

The square root of 84781 is about 291.1717706097. The cubic root of 84781 is about 43.9305032373.

The spelling of 84781 in words is "eighty-four thousand, seven hundred eighty-one".