6665106561661 has 2 divisors, whose sum is σ = 6665106561662. Its totient is φ = 6665106561660.

The previous prime is 6665106561559. The next prime is 6665106561677. The reversal of 6665106561661 is 1661656015666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5106216973636 + 1558889588025 = 2259694^2 + 1248555^2 .

It is a cyclic number.

It is not a de Polignac number, because 6665106561661 - 2²⁹ = 6664569690749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6665106561691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3332553280830 + 3332553280831.

It is an arithmetic number, because the mean of its divisors is an integer number (3332553280831).

Almost surely, 2^{6665106561661} is an apocalyptic number.

It is an amenable number.

6665106561661 is a deficient number, since it is larger than the sum of its proper divisors (1).

6665106561661 is an equidigital number, since it uses as much as digits as its factorization.

6665106561661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6998400, while the sum is 55.

The spelling of 6665106561661 in words is "six trillion, six hundred sixty-five billion, one hundred six million, five hundred sixty-one thousand, six hundred sixty-one".