161731540 has 24 divisors (see below), whose sum is σ = 359615592. Its totient is φ = 60887040.

The previous prime is 161731529. The next prime is 161731543. The reversal of 161731540 is 45137161.

It can be written as a sum of positive squares in 4 ways, for example, as 43270084 + 118461456 = 6578^2 + 10884^2 .

It is a junction number, because it is equal to n+sod(n) for n = 161731499 and 161731508.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161731543) 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, 237501 + ... + 238180.

It is an arithmetic number, because the mean of its divisors is an integer number (14983983).

Almost surely, 2^161731540 is an apocalyptic number.

161731540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161731540 is an abundant number, since it is smaller than the sum of its proper divisors (197884052).

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

161731540 is a wasteful number, since it uses less digits than its factorization.

161731540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 475707 (or 475705 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 161731540 is about 12717.3715837826. The cubic root of 161731540 is about 544.8348853124.

The spelling of 161731540 in words is "one hundred sixty-one million, seven hundred thirty-one thousand, five hundred forty".