161919820 has 48 divisors (see below), whose sum is σ = 353203200. Its totient is φ = 62285760.

The previous prime is 161919809. The next prime is 161919833. The reversal of 161919820 is 28919161.

161919820 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 161919820.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 110251 + ... + 111709.

It is an arithmetic number, because the mean of its divisors is an integer number (7358400).

Almost surely, 2^161919820 is an apocalyptic number.

161919820 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 161919820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (176601600).

161919820 is an abundant number, since it is smaller than the sum of its proper divisors (191283380).

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

161919820 is a wasteful number, since it uses less digits than its factorization.

161919820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1678 (or 1676 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 37.

The square root of 161919820 is about 12724.7719036531. The cubic root of 161919820 is about 545.0462267554.

The spelling of 161919820 in words is "one hundred sixty-one million, nine hundred nineteen thousand, eight hundred twenty".