2181686809 has 2 divisors, whose sum is σ = 2181686810. Its totient is φ = 2181686808.

The previous prime is 2181686797. The next prime is 2181686851. The reversal of 2181686809 is 9086861812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2111126809 + 70560000 = 45947^2 + 8400^2 .

It is a cyclic number.

It is not a de Polignac number, because 2181686809 - 2⁷ = 2181686681 is a prime.

It is not a weakly prime, because it can be changed into another prime (2181686209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1090843404 + 1090843405.

It is an arithmetic number, because the mean of its divisors is an integer number (1090843405).

Almost surely, 2^2181686809 is an apocalyptic number.

It is an amenable number.

2181686809 is a deficient number, since it is larger than the sum of its proper divisors (1).

2181686809 is an equidigital number, since it uses as much as digits as its factorization.

2181686809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 331776, while the sum is 49.

The square root of 2181686809 is about 46708.5303665187. The cubic root of 2181686809 is about 1296.9726021121.

The spelling of 2181686809 in words is "two billion, one hundred eighty-one million, six hundred eighty-six thousand, eight hundred nine".