161821793940 has 96 divisors (see below), whose sum is σ = 468922608000. Its totient is φ = 41646915072.

The previous prime is 161821793929. The next prime is 161821793941. The reversal of 161821793940 is 49397128161.

161821793940 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161821793941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4399546 + ... + 4436174.

It is an arithmetic number, because the mean of its divisors is an integer number (4884610500).

Almost surely, 2^161821793940 is an apocalyptic number.

161821793940 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 161821793940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (234461304000).

161821793940 is an abundant number, since it is smaller than the sum of its proper divisors (307100814060).

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

161821793940 is a wasteful number, since it uses less digits than its factorization.

161821793940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39209 (or 39207 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 51.

The spelling of 161821793940 in words is "one hundred sixty-one billion, eight hundred twenty-one million, seven hundred ninety-three thousand, nine hundred forty".