161281387520 has 352 divisors, whose sum is σ = 463658273280. Its totient is φ = 53137244160.

The previous prime is 161281387511. The next prime is 161281387523. The reversal of 161281387520 is 25783182161.

It is a tau number, because it is divible by the number of its divisors (352).

It is a Harshad number since it is a multiple of its sum of digits (44).

It is not an unprimeable number, because it can be changed into a prime (161281387523) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 24608564 + ... + 24615116.

Almost surely, 2^161281387520 is an apocalyptic number.

161281387520 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 161281387520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (231829136640).

161281387520 is an abundant number, since it is smaller than the sum of its proper divisors (302376885760).

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

161281387520 is a wasteful number, since it uses less digits than its factorization.

161281387520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6631 (or 6613 counting only the distinct ones).

The product of its (nonzero) digits is 161280, while the sum is 44.

The spelling of 161281387520 in words is "one hundred sixty-one billion, two hundred eighty-one million, three hundred eighty-seven thousand, five hundred twenty".