99781 has 8 divisors (see below), whose sum is σ = 111744. Its totient is φ = 88320.

The previous prime is 99767. The next prime is 99787. The reversal of 99781 is 18799.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-99781 is a prime.

It is a super-3 number, since 3×99781³ = 2980333133389623, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

99781 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99787) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 421 + ... + 613.

It is an arithmetic number, because the mean of its divisors is an integer number (13968).

2⁹⁹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

99781 is a deficient number, since it is larger than the sum of its proper divisors (11963).

99781 is a wasteful number, since it uses less digits than its factorization.

99781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251.

The product of its digits is 4536, while the sum is 34.

The square root of 99781 is about 315.8813068227. The cubic root of 99781 is about 46.3819799725.

The spelling of 99781 in words is "ninety-nine thousand, seven hundred eighty-one".