161668664820 has 432 divisors, whose sum is σ = 577940060880. Its totient is φ = 36237680640.

The previous prime is 161668664771. The next prime is 161668664821. The reversal of 161668664820 is 28466866161.

It can be written as a sum of positive squares in 8 ways, for example, as 9390772836 + 152277891984 = 96906^2 + 390228^2 .

It is a super-2 number, since 2×161668664820² (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 (161668664821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 38226466 + ... + 38230694.

It is an arithmetic number, because the mean of its divisors is an integer number (1337824215).

Almost surely, 2^161668664820 is an apocalyptic number.

161668664820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 161668664820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (288970030440).

161668664820 is an abundant number, since it is smaller than the sum of its proper divisors (416271396060).

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

161668664820 is a wasteful number, since it uses less digits than its factorization.

161668664820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4336 (or 4300 counting only the distinct ones).

The product of its (nonzero) digits is 3981312, while the sum is 54.

The spelling of 161668664820 in words is "one hundred sixty-one billion, six hundred sixty-eight million, six hundred sixty-four thousand, eight hundred twenty".