161981977762388 has 108 divisors (see below), whose sum is σ = 348301028667060. Its totient is φ = 65713570804224.

The previous prime is 161981977762321. The next prime is 161981977762399. The reversal of 161981977762388 is 883267779189161.

161981977762388 is digitally balanced in base 2, 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 2 ways, for example, as 151037512631824 + 10944465130564 = 12289732^2 + 3308242^2 .

It is a super-2 number, since 2×161981977762388² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 86027756 + ... + 87890492.

It is an arithmetic number, because the mean of its divisors is an integer number (3225009524695).

Almost surely, 2^{161981977762388} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 161981977762388, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (174150514333530).

161981977762388 is an abundant number, since it is smaller than the sum of its proper divisors (186319050904672).

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

161981977762388 is a wasteful number, since it uses less digits than its factorization.

161981977762388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1864022 (or 1863994 counting only the distinct ones).

The product of its digits is 3072577536, while the sum is 83.

The spelling of 161981977762388 in words is "one hundred sixty-one trillion, nine hundred eighty-one billion, nine hundred seventy-seven million, seven hundred sixty-two thousand, three hundred eighty-eight".