161899920 has 360 divisors, whose sum is σ = 683065656. Its totient is φ = 34062336.

The previous prime is 161899879. The next prime is 161899943. The reversal of 161899920 is 29998161.

161899920 is a `hidden beast` number, since 1 + 618 + 9 + 9 + 9 + 20 = 666.

161899920 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 1016064 + 160883856 = 1008^2 + 12684^2 .

It is a tau number, because it is divible by the number of its divisors (360).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 458464 + ... + 458816.

Almost surely, 2^161899920 is an apocalyptic number.

161899920 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 161899920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (341532828).

161899920 is an abundant number, since it is smaller than the sum of its proper divisors (521165736).

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

161899920 is a wasteful number, since it uses less digits than its factorization.

161899920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399 (or 383 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 45.

The square root of 161899920 is about 12723.9899402664. The cubic root of 161899920 is about 545.0238970528.

The spelling of 161899920 in words is "one hundred sixty-one million, eight hundred ninety-nine thousand, nine hundred twenty".