2185521991 has 2 divisors, whose sum is σ = 2185521992. Its totient is φ = 2185521990.

The previous prime is 2185521971. The next prime is 2185522013. The reversal of 2185521991 is 1991255812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2185521991 - 2¹¹ = 2185519943 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2185521901) 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, 1092760995 + 1092760996.

It is an arithmetic number, because the mean of its divisors is an integer number (1092760996).

Almost surely, 2^2185521991 is an apocalyptic number.

2185521991 is a deficient number, since it is larger than the sum of its proper divisors (1).

2185521991 is an equidigital number, since it uses as much as digits as its factorization.

2185521991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64800, while the sum is 43.

The square root of 2185521991 is about 46749.5667466555. The cubic root of 2185521991 is about 1297.7321388969.

It can be divided in two parts, 2185 and 521991, that added together give a square (524176 = 724²).

The spelling of 2185521991 in words is "two billion, one hundred eighty-five million, five hundred twenty-one thousand, nine hundred ninety-one".