2661171991 has 2 divisors, whose sum is σ = 2661171992. Its totient is φ = 2661171990.

The previous prime is 2661171973. The next prime is 2661172039. The reversal of 2661171991 is 1991711662.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2661171991 - 2¹⁷ = 2661040919 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2661171971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330585995 + 1330585996.

It is an arithmetic number, because the mean of its divisors is an integer number (1330585996).

Almost surely, 2^2661171991 is an apocalyptic number.

2661171991 is a deficient number, since it is larger than the sum of its proper divisors (1).

2661171991 is an equidigital number, since it uses as much as digits as its factorization.

2661171991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 40824, while the sum is 43.

The square root of 2661171991 is about 51586.5485470777. The cubic root of 2661171991 is about 1385.7694449461.

The spelling of 2661171991 in words is "two billion, six hundred sixty-one million, one hundred seventy-one thousand, nine hundred ninety-one".