2181138391 has 2 divisors, whose sum is σ = 2181138392. Its totient is φ = 2181138390.

The previous prime is 2181138361. The next prime is 2181138469. The reversal of 2181138391 is 1938311812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2181138391 - 2²⁹ = 1644267479 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2181138391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2181138361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1090569195 + 1090569196.

It is an arithmetic number, because the mean of its divisors is an integer number (1090569196).

Almost surely, 2^2181138391 is an apocalyptic number.

2181138391 is a deficient number, since it is larger than the sum of its proper divisors (1).

2181138391 is an equidigital number, since it uses as much as digits as its factorization.

2181138391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 37.

The square root of 2181138391 is about 46702.6593568289. The cubic root of 2181138391 is about 1296.8639182068.

It can be divided in two parts, 2181138 and 391, that added together give a square (2181529 = 1477²).

The spelling of 2181138391 in words is "two billion, one hundred eighty-one million, one hundred thirty-eight thousand, three hundred ninety-one".