161665566501 has 16 divisors (see below), whose sum is σ = 218806783488. Its totient is φ = 106151218800.

The previous prime is 161665566481. The next prime is 161665566523. The reversal of 161665566501 is 105665566161.

It is not a de Polignac number, because 161665566501 - 2¹⁹ = 161665042213 is a prime.

It is a super-2 number, since 2×161665566501² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161665516501) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1242736 + ... + 1366646.

It is an arithmetic number, because the mean of its divisors is an integer number (13675423968).

Almost surely, 2^161665566501 is an apocalyptic number.

It is an amenable number.

161665566501 is a deficient number, since it is larger than the sum of its proper divisors (57141216987).

161665566501 is a wasteful number, since it uses less digits than its factorization.

161665566501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130472.

The product of its (nonzero) digits is 972000, while the sum is 48.

The spelling of 161665566501 in words is "one hundred sixty-one billion, six hundred sixty-five million, five hundred sixty-six thousand, five hundred one".