398640 has 80 divisors (see below), whose sum is σ = 1357056. Its totient is φ = 96000.

The previous prime is 398627. The next prime is 398669. The reversal of 398640 is 46893.

398640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 398598 and 398607.

It is an unprimeable number.

398640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2565 + ... + 2715.

398640 is a Friedman number, since it can be written as 60*(83+9^4), using all its digits and the basic arithmetic operations.

2³⁹⁸⁶⁴⁰ is an apocalyptic number.

398640 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 398640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (678528).

398640 is an abundant number, since it is smaller than the sum of its proper divisors (958416).

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

398640 is a wasteful number, since it uses less digits than its factorization.

398640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178 (or 172 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 398640 is about 631.3794421740. The cubic root of 398640 is about 73.5970304410.

The spelling of 398640 in words is "three hundred ninety-eight thousand, six hundred forty".