243981 has 6 divisors (see below), whose sum is σ = 352430. Its totient is φ = 162648.

The previous prime is 243973. The next prime is 243989. The reversal of 243981 is 189342.

It is an interprime number because it is at equal distance from previous prime (243973) and next prime (243989).

It can be written as a sum of positive squares in only one way, i.e., 189225 + 54756 = 435^2 + 234^2 .

It is not a de Polignac number, because 243981 - 2³ = 243973 is a prime.

It is a super-2 number, since 2×243981² = 119053456722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (243989) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13546 + ... + 13563.

2²⁴³⁹⁸¹ is an apocalyptic number.

It is an amenable number.

243981 is a deficient number, since it is larger than the sum of its proper divisors (108449).

243981 is a wasteful number, since it uses less digits than its factorization.

243981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27115 (or 27112 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 243981 is about 493.9443288469. The cubic root of 243981 is about 62.4863756969.

It can be divided in two parts, 24 and 3981, that added together give a triangular number (4005 = T₈₉).

The spelling of 243981 in words is "two hundred forty-three thousand, nine hundred eighty-one".