381681 has 6 divisors (see below), whose sum is σ = 551330. Its totient is φ = 254448.

The previous prime is 381673. The next prime is 381697. The reversal of 381681 is 186183.

It can be written as a sum of positive squares in only one way, i.e., 349281 + 32400 = 591^2 + 180^2 .

It is not a de Polignac number, because 381681 - 2³ = 381673 is a prime.

It is a super-2 number, since 2×381681² = 291360771522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (381631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 21196 + ... + 21213.

2³⁸¹⁶⁸¹ is an apocalyptic number.

It is an amenable number.

381681 is a deficient number, since it is larger than the sum of its proper divisors (169649).

381681 is a wasteful number, since it uses less digits than its factorization.

381681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42415 (or 42412 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 381681 is about 617.8033667762. The cubic root of 381681 is about 72.5382121194.

The spelling of 381681 in words is "three hundred eighty-one thousand, six hundred eighty-one".