1728161381 has 4 divisors (see below), whose sum is σ = 1731557100. Its totient is φ = 1724765664.

The previous prime is 1728161363. The next prime is 1728161399. The reversal of 1728161381 is 1831618271.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (1728161363) and next prime (1728161399).

It can be written as a sum of positive squares in 2 ways, for example, as 1426270756 + 301890625 = 37766^2 + 17375^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1728161381 is a prime.

It is a super-2 number, since 2×1728161381² = 5973083517559654322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1728161311) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1697096 + ... + 1698113.

It is an arithmetic number, because the mean of its divisors is an integer number (432889275).

Almost surely, 2^1728161381 is an apocalyptic number.

It is an amenable number.

1728161381 is a deficient number, since it is larger than the sum of its proper divisors (3395719).

1728161381 is an equidigital number, since it uses as much as digits as its factorization.

1728161381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3395718.

The product of its digits is 16128, while the sum is 38.

The square root of 1728161381 is about 41571.1604480799. The cubic root of 1728161381 is about 1200.0373555501.

The spelling of 1728161381 in words is "one billion, seven hundred twenty-eight million, one hundred sixty-one thousand, three hundred eighty-one".