11666166601561 has 2 divisors, whose sum is σ = 11666166601562. Its totient is φ = 11666166601560.

The previous prime is 11666166601501. The next prime is 11666166601597. The reversal of 11666166601561 is 16510666166611.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7709174371600 + 3956992229961 = 2776540^2 + 1989219^2 .

It is a cyclic number.

It is not a de Polignac number, because 11666166601561 - 2¹⁷ = 11666166470489 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 11666166601499 and 11666166601508.

It is not a weakly prime, because it can be changed into another prime (11666166601501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5833083300780 + 5833083300781.

It is an arithmetic number, because the mean of its divisors is an integer number (5833083300781).

Almost surely, 2^{11666166601561} is an apocalyptic number.

It is an amenable number.

11666166601561 is a deficient number, since it is larger than the sum of its proper divisors (1).

11666166601561 is an equidigital number, since it uses as much as digits as its factorization.

11666166601561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1399680, while the sum is 52.

The spelling of 11666166601561 in words is "eleven trillion, six hundred sixty-six billion, one hundred sixty-six million, six hundred one thousand, five hundred sixty-one".