2166511261 has 2 divisors, whose sum is σ = 2166511262. Its totient is φ = 2166511260.

The previous prime is 2166511189. The next prime is 2166511273. The reversal of 2166511261 is 1621156612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1795216900 + 371294361 = 42370^2 + 19269^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2166511261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2166518261) 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, 1083255630 + 1083255631.

It is an arithmetic number, because the mean of its divisors is an integer number (1083255631).

Almost surely, 2^2166511261 is an apocalyptic number.

It is an amenable number.

2166511261 is a deficient number, since it is larger than the sum of its proper divisors (1).

2166511261 is an equidigital number, since it uses as much as digits as its factorization.

2166511261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 2166511261 is about 46545.7974579875. The cubic root of 2166511261 is about 1293.9584079425.

Adding to 2166511261 its reverse (1621156612), we get a palindrome (3787667873).

The spelling of 2166511261 in words is "two billion, one hundred sixty-six million, five hundred eleven thousand, two hundred sixty-one".