161565505011 has 24 divisors (see below), whose sum is σ = 241849713840. Its totient is φ = 106599753216.

The previous prime is 161565505007. The next prime is 161565505109. The reversal of 161565505011 is 110505565161.

It is a happy number.

161565505011 is a `hidden beast` number, since 1 + 6 + 1 + 56 + 550 + 50 + 1 + 1 = 666.

It is not a de Polignac number, because 161565505011 - 2² = 161565505007 is a prime.

It is a super-2 number, since 2×161565505011² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (161565505411) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 63946 + ... + 572031.

It is an arithmetic number, because the mean of its divisors is an integer number (10077071410).

Almost surely, 2^161565505011 is an apocalyptic number.

161565505011 is a deficient number, since it is larger than the sum of its proper divisors (80284208829).

161565505011 is an frugal number, since it uses more digits than its factorization.

161565505011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636180 (or 636077 counting only the distinct ones).

The product of its (nonzero) digits is 22500, while the sum is 36.

The spelling of 161565505011 in words is "one hundred sixty-one billion, five hundred sixty-five million, five hundred five thousand, eleven".