249661 has 4 divisors (see below), whose sum is σ = 258300. Its totient is φ = 241024.

The previous prime is 249659. The next prime is 249671. The reversal of 249661 is 166942.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166942 = 2 ⋅83471.

It can be written as a sum of positive squares in 2 ways, for example, as 93636 + 156025 = 306^2 + 395^2 .

It is a cyclic number.

It is not a de Polignac number, because 249661 - 2¹ = 249659 is a prime.

It is a super-2 number, since 2×249661² = 124661229842, which contains 22 as substring.

It is a Duffinian number.

249661 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (249671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4276 + ... + 4333.

It is an arithmetic number, because the mean of its divisors is an integer number (64575).

2²⁴⁹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

249661 is a deficient number, since it is larger than the sum of its proper divisors (8639).

249661 is an equidigital number, since it uses as much as digits as its factorization.

249661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8638.

The product of its digits is 2592, while the sum is 28.

The square root of 249661 is about 499.6608850010. The cubic root of 249661 is about 62.9675653990.

The spelling of 249661 in words is "two hundred forty-nine thousand, six hundred sixty-one".