381661 has 6 divisors (see below), whose sum is σ = 444030. Its totient is φ = 327096.

The previous prime is 381659. The next prime is 381673. The reversal of 381661 is 166183.

It can be written as a sum of positive squares in only one way, i.e., 337561 + 44100 = 581^2 + 210^2 .

It is not a de Polignac number, because 381661 - 2¹ = 381659 is a prime.

It is a Duffinian number.

It is a congruent number.

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

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3846 + ... + 3943.

It is an arithmetic number, because the mean of its divisors is an integer number (74005).

2³⁸¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

381661 is a deficient number, since it is larger than the sum of its proper divisors (62369).

381661 is an equidigital number, since it uses as much as digits as its factorization.

381661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7803 (or 7796 counting only the distinct ones).

The product of its digits is 864, while the sum is 25.

The square root of 381661 is about 617.7871801842. The cubic root of 381661 is about 72.5369451019.

The spelling of 381661 in words is "three hundred eighty-one thousand, six hundred sixty-one".