2181357691 has 2 divisors, whose sum is σ = 2181357692. Its totient is φ = 2181357690.

The previous prime is 2181357677. The next prime is 2181357713. The reversal of 2181357691 is 1967531812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2181357691 - 2⁹ = 2181357179 is a prime.

It is not a weakly prime, because it can be changed into another prime (2181354691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1090678845 + 1090678846.

It is an arithmetic number, because the mean of its divisors is an integer number (1090678846).

Almost surely, 2^2181357691 is an apocalyptic number.

2181357691 is a deficient number, since it is larger than the sum of its proper divisors (1).

2181357691 is an equidigital number, since it uses as much as digits as its factorization.

2181357691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 90720, while the sum is 43.

The square root of 2181357691 is about 46705.0071298571. The cubic root of 2181357691 is about 1296.9073806371.

The spelling of 2181357691 in words is "two billion, one hundred eighty-one million, three hundred fifty-seven thousand, six hundred ninety-one".