640381 has 8 divisors (see below), whose sum is σ = 747200. Its totient is φ = 548604.

The previous prime is 640369. The next prime is 640411. The reversal of 640381 is 183046.

It is not a de Polignac number, because 640381 - 2¹³ = 632189 is a prime.

It is a super-2 number, since 2×640381² = 820175650322, which contains 22 as substring.

It is a Duffinian number.

640381 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644381) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 591 + ... + 1276.

It is an arithmetic number, because the mean of its divisors is an integer number (93400).

2⁶⁴⁰³⁸¹ is an apocalyptic number.

It is an amenable number.

640381 is a deficient number, since it is larger than the sum of its proper divisors (106819).

640381 is an equidigital number, since it uses as much as digits as its factorization.

640381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1888 (or 1874 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 640381 is about 800.2380895708. The cubic root of 640381 is about 86.1944850343.

The spelling of 640381 in words is "six hundred forty thousand, three hundred eighty-one".