161605221128 has 100 divisors (see below), whose sum is σ = 339983266215. Its totient is φ = 72015058752.

The previous prime is 161605221077. The next prime is 161605221137. The reversal of 161605221128 is 821122506161.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 13 ways, for example, as 161152467844 + 452753284 = 401438^2 + 21278^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=284258.

It is a super-2 number, since 2×161605221128² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 24 ways as a sum of consecutive naturals, for example, 5572593818 + ... + 5572593846.

Almost surely, 2^161605221128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 161605221128

161605221128 is an abundant number, since it is smaller than the sum of its proper divisors (178378045087).

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

161605221128 is an frugal number, since it uses more digits than its factorization.

161605221128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174 (or 44 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 35.

Adding to 161605221128 its reverse (821122506161), we get a palindrome (982727727289).

The spelling of 161605221128 in words is "one hundred sixty-one billion, six hundred five million, two hundred twenty-one thousand, one hundred twenty-eight".