381721 has 4 divisors (see below), whose sum is σ = 386100. Its totient is φ = 377344.

The previous prime is 381713. The next prime is 381737. The reversal of 381721 is 127183.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 127183 = 7 ⋅18169.

It can be written as a sum of positive squares in 2 ways, for example, as 230400 + 151321 = 480^2 + 389^2 .

It is a cyclic number.

It is not a de Polignac number, because 381721 - 2³ = 381713 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 381692 and 381701.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (381761) 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, 2056 + ... + 2233.

It is an arithmetic number, because the mean of its divisors is an integer number (96525).

2³⁸¹⁷²¹ is an apocalyptic number.

It is an amenable number.

381721 is a deficient number, since it is larger than the sum of its proper divisors (4379).

381721 is an equidigital number, since it uses as much as digits as its factorization.

381721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4378.

The product of its digits is 336, while the sum is 22.

The square root of 381721 is about 617.8357386879. The cubic root of 381721 is about 72.5407460218.

The spelling of 381721 in words is "three hundred eighty-one thousand, seven hundred twenty-one".