2188781 has 12 divisors (see below), whose sum is σ = 2681280. Its totient is φ = 1776600.

The previous prime is 2188757. The next prime is 2188783. The reversal of 2188781 is 1878812.

It is not a de Polignac number, because 2188781 - 2¹⁴ = 2172397 is a prime.

It is a super-2 number, since 2×2188781² = 9581524531922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2188783) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 245 + ... + 2106.

It is an arithmetic number, because the mean of its divisors is an integer number (223440).

2^2188781 is an apocalyptic number.

It is an amenable number.

2188781 is a deficient number, since it is larger than the sum of its proper divisors (492499).

2188781 is a wasteful number, since it uses less digits than its factorization.

2188781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2384 (or 2377 counting only the distinct ones).

The product of its digits is 7168, while the sum is 35.

The square root of 2188781 is about 1479.4529394340. The cubic root of 2188781 is about 129.8376869729.

The spelling of 2188781 in words is "two million, one hundred eighty-eight thousand, seven hundred eighty-one".