2218781 has 4 divisors (see below), whose sum is σ = 2228700. Its totient is φ = 2208864.

The previous prime is 2218771. The next prime is 2218807. The reversal of 2218781 is 1878122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1878122 = 2 ⋅939061.

It can be written as a sum of positive squares in 2 ways, for example, as 1716100 + 502681 = 1310^2 + 709^2 .

It is a cyclic number.

It is not a de Polignac number, because 2218781 - 2¹⁰ = 2217757 is a prime.

It is a super-2 number, since 2×2218781² = 9845978251922, 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 (2218751) 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, 4616 + ... + 5073.

It is an arithmetic number, because the mean of its divisors is an integer number (557175).

2^2218781 is an apocalyptic number.

It is an amenable number.

2218781 is a deficient number, since it is larger than the sum of its proper divisors (9919).

2218781 is an equidigital number, since it uses as much as digits as its factorization.

2218781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9918.

The product of its digits is 1792, while the sum is 29.

The square root of 2218781 is about 1489.5573167891. The cubic root of 2218781 is about 130.4281935915.

The spelling of 2218781 in words is "two million, two hundred eighteen thousand, seven hundred eighty-one".