161561216 has 32 divisors (see below), whose sum is σ = 325072980. Its totient is φ = 79974400.

The previous prime is 161561209. The next prime is 161561221. The reversal of 161561216 is 612165161.

It can be written as a sum of positive squares in 2 ways, for example, as 146506816 + 15054400 = 12104^2 + 3880^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is a super-2 number, since 2×161561216² = 52204053030797312, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6680 + ... + 19176.

Almost surely, 2^161561216 is an apocalyptic number.

161561216 is a gapful number since it is divisible by the number (16) 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 161561216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (162536490).

161561216 is an abundant number, since it is smaller than the sum of its proper divisors (163511764).

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

161561216 is a wasteful number, since it uses less digits than its factorization.

161561216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12612 (or 12600 counting only the distinct ones).

The product of its digits is 2160, while the sum is 29.

The square root of 161561216 is about 12710.6733102539. The cubic root of 161561216 is about 544.6435578564.

The spelling of 161561216 in words is "one hundred sixty-one million, five hundred sixty-one thousand, two hundred sixteen".