2099781 has 12 divisors (see below), whose sum is σ = 3052140. Its totient is φ = 1391040.

The previous prime is 2099771. The next prime is 2099809. The reversal of 2099781 is 1879902.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 695556 + 1404225 = 834^2 + 1185^2 .

It is not a de Polignac number, because 2099781 - 2⁵ = 2099749 is a prime.

It is a super-2 number, since 2×2099781² = 8818160495922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is an Ulam number.

It is a Curzon number.

2099781 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2099711) 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, 985 + ... + 2273.

It is an arithmetic number, because the mean of its divisors is an integer number (254345).

2^2099781 is an apocalyptic number.

It is an amenable number.

2099781 is a deficient number, since it is larger than the sum of its proper divisors (952359).

2099781 is a wasteful number, since it uses less digits than its factorization.

2099781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1476 (or 1473 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 2099781 is about 1449.0621104701. The cubic root of 2099781 is about 128.0534648069.

The spelling of 2099781 in words is "two million, ninety-nine thousand, seven hundred eighty-one".