1581381 has 6 divisors (see below), whose sum is σ = 2284230. Its totient is φ = 1054248.

The previous prime is 1581379. The next prime is 1581413. The reversal of 1581381 is 1831851.

1581381 is a `hidden beast` number, since 1 + 581 + 3 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1232100 + 349281 = 1110^2 + 591^2 .

It is not a de Polignac number, because 1581381 - 2¹ = 1581379 is a prime.

It is a super-3 number, since 3×1581381³ = 11863990883330788023, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1581311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 87846 + ... + 87863.

It is an arithmetic number, because the mean of its divisors is an integer number (380705).

2^1581381 is an apocalyptic number.

It is an amenable number.

1581381 is a deficient number, since it is larger than the sum of its proper divisors (702849).

1581381 is a wasteful number, since it uses less digits than its factorization.

1581381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 175715 (or 175712 counting only the distinct ones).

The product of its digits is 960, while the sum is 27.

The square root of 1581381 is about 1257.5297213187. The cubic root of 1581381 is about 116.5052525154.

The spelling of 1581381 in words is "one million, five hundred eighty-one thousand, three hundred eighty-one".