161665920 has 384 divisors, whose sum is σ = 641571840. Its totient is φ = 37158912.

The previous prime is 161665897. The next prime is 161665951. The reversal of 161665920 is 29566161.

161665920 is a `hidden beast` number, since 1 + 6 + 1 + 66 + 592 + 0 = 666.

161665920 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (384).

It is a super-3 number, since 3×161665920³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 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 pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1272897 + ... + 1273023.

It is an arithmetic number, because the mean of its divisors is an integer number (1670760).

Almost surely, 2^161665920 is an apocalyptic number.

161665920 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 161665920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (320785920).

161665920 is an abundant number, since it is smaller than the sum of its proper divisors (479905920).

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

161665920 is a wasteful number, since it uses less digits than its factorization.

161665920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182 (or 167 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 161665920 is about 12714.7913864129. The cubic root of 161665920 is about 544.7611893148.

The spelling of 161665920 in words is "one hundred sixty-one million, six hundred sixty-five thousand, nine hundred twenty".