161881920 has 84 divisors (see below), whose sum is σ = 556816260. Its totient is φ = 43167744.

The previous prime is 161881901. The next prime is 161881933. The reversal of 161881920 is 29188161.

161881920 is a `hidden beast` number, since 1 + 618 + 8 + 19 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 88059456 + 73822464 = 9384^2 + 8592^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 25225 + ... + 30984.

It is an arithmetic number, because the mean of its divisors is an integer number (6628765).

Almost surely, 2^161881920 is an apocalyptic number.

161881920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161881920 is an abundant number, since it is smaller than the sum of its proper divisors (394934340).

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

161881920 is a wasteful number, since it uses less digits than its factorization.

161881920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56232 (or 56219 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 36.

The square root of 161881920 is about 12723.2825953053. The cubic root of 161881920 is about 545.0036977557.

It can be divided in two parts, 1618 and 81920, that added together give a palindrome (83538).

The spelling of 161881920 in words is "one hundred sixty-one million, eight hundred eighty-one thousand, nine hundred twenty".