161666506665 has 32 divisors (see below), whose sum is σ = 295174892160. Its totient is φ = 83891806272.

The previous prime is 161666506663. The next prime is 161666506669. The reversal of 161666506665 is 566605666161.

It is not a de Polignac number, because 161666506665 - 2¹ = 161666506663 is a prime.

It is a super-2 number, since 2×161666506665² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (161666506663) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 16177839 + ... + 16187828.

It is an arithmetic number, because the mean of its divisors is an integer number (9224215380).

Almost surely, 2^161666506665 is an apocalyptic number.

161666506665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

161666506665 is a deficient number, since it is larger than the sum of its proper divisors (133508385495).

161666506665 is a wasteful number, since it uses less digits than its factorization.

161666506665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32365718 (or 32365712 counting only the distinct ones).

The product of its (nonzero) digits is 6998400, while the sum is 54.

It can be divided in two parts, 161666506 and 665, that added together give a triangular number (161667171 = T₁₇₉₈₁).

The spelling of 161666506665 in words is "one hundred sixty-one billion, six hundred sixty-six million, five hundred six thousand, six hundred sixty-five".