2199781 has 2 divisors, whose sum is σ = 2199782. Its totient is φ = 2199780.

The previous prime is 2199739. The next prime is 2199803. The reversal of 2199781 is 1879912.

It is the 606-th star number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2149156 + 50625 = 1466^2 + 225^2 .

It is a cyclic number.

It is not a de Polignac number, because 2199781 - 2⁷ = 2199653 is a prime.

It is a super-2 number, since 2×2199781² = 9678072895922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 2199781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2199181) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1099890 + 1099891.

It is an arithmetic number, because the mean of its divisors is an integer number (1099891).

2^2199781 is an apocalyptic number.

It is an amenable number.

2199781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2199781 is an equidigital number, since it uses as much as digits as its factorization.

2199781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 37.

The square root of 2199781 is about 1483.1658706969. The cubic root of 2199781 is about 130.0548289430.

It can be divided in two parts, 219 and 9781, that added together give a 4-th power (10000 = 10⁴).

The spelling of 2199781 in words is "two million, one hundred ninety-nine thousand, seven hundred eighty-one".