165557121205566 has 16 divisors (see below), whose sum is σ = 331135936510464. Its totient is φ = 55182091385304.

The previous prime is 165557121205529. The next prime is 165557121205603. The reversal of 165557121205566 is 665502121755561.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (165557121205529) and next prime (165557121205603).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 903821596 + ... + 904004751.

It is an arithmetic number, because the mean of its divisors is an integer number (20695996031904).

Almost surely, 2^{165557121205566} is an apocalyptic number.

165557121205566 is an abundant number, since it is smaller than the sum of its proper divisors (165578815304898).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

165557121205566 is a wasteful number, since it uses less digits than its factorization.

165557121205566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1807841615.

The product of its (nonzero) digits is 18900000, while the sum is 57.

The spelling of 165557121205566 in words is "one hundred sixty-five trillion, five hundred fifty-seven billion, one hundred twenty-one million, two hundred five thousand, five hundred sixty-six".