393640 has 32 divisors (see below), whose sum is σ = 955080. Its totient is φ = 145152.

The previous prime is 393637. The next prime is 393649. The reversal of 393640 is 46393.

It can be written as a sum of positive squares in 4 ways, for example, as 268324 + 125316 = 518^2 + 354^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (393649) 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, 142 + ... + 898.

2³⁹³⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 393640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (477540).

393640 is an abundant number, since it is smaller than the sum of its proper divisors (561440).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

393640 is a wasteful number, since it uses less digits than its factorization.

393640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 781 (or 777 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 25.

The square root of 393640 is about 627.4073636801. The cubic root of 393640 is about 73.2880344667.

The spelling of 393640 in words is "three hundred ninety-three thousand, six hundred forty".