161123891540 has 24 divisors (see below), whose sum is σ = 350027765640. Its totient is φ = 62227157888.

The previous prime is 161123891479. The next prime is 161123891543. The reversal of 161123891540 is 45198321161.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 17441956624 + 143681934916 = 132068^2 + 379054^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161123891543) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 138899327 + ... + 138900486.

It is an arithmetic number, because the mean of its divisors is an integer number (14584490235).

Almost surely, 2^161123891540 is an apocalyptic number.

161123891540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161123891540 is an abundant number, since it is smaller than the sum of its proper divisors (188903874100).

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

161123891540 is a wasteful number, since it uses less digits than its factorization.

161123891540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 277799851 (or 277799849 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 41.

The spelling of 161123891540 in words is "one hundred sixty-one billion, one hundred twenty-three million, eight hundred ninety-one thousand, five hundred forty".