1665610515181 has 2 divisors, whose sum is σ = 1665610515182. Its totient is φ = 1665610515180.

The previous prime is 1665610515131. The next prime is 1665610515211. The reversal of 1665610515181 is 1815150165661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1604361689956 + 61248825225 = 1266634^2 + 247485^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665610515181 - 2¹⁵ = 1665610482413 is a prime.

It is a super-2 number, since 2×1665610515181² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665610515131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832805257590 + 832805257591.

It is an arithmetic number, because the mean of its divisors is an integer number (832805257591).

Almost surely, 2^{1665610515181} is an apocalyptic number.

It is an amenable number.

1665610515181 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665610515181 is an equidigital number, since it uses as much as digits as its factorization.

1665610515181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216000, while the sum is 46.

The spelling of 1665610515181 in words is "one trillion, six hundred sixty-five billion, six hundred ten million, five hundred fifteen thousand, one hundred eighty-one".