161728720 has 20 divisors (see below), whose sum is σ = 376019460. Its totient is φ = 64691456.

The previous prime is 161728717. The next prime is 161728733. The reversal of 161728720 is 27827161.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 37896336 + 123832384 = 6156^2 + 11128^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

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, 1010725 + ... + 1010884.

It is an arithmetic number, because the mean of its divisors is an integer number (18800973).

Almost surely, 2^161728720 is an apocalyptic number.

161728720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161728720 is an abundant number, since it is smaller than the sum of its proper divisors (214290740).

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

161728720 is a wasteful number, since it uses less digits than its factorization.

161728720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2021622 (or 2021616 counting only the distinct ones).

The product of its (nonzero) digits is 9408, while the sum is 34.

The square root of 161728720 is about 12717.2607113325. The cubic root of 161728720 is about 544.8317186587.

The spelling of 161728720 in words is "one hundred sixty-one million, seven hundred twenty-eight thousand, seven hundred twenty".