406640 has 80 divisors (see below), whose sum is σ = 1124928. Its totient is φ = 135168.

The previous prime is 406633. The next prime is 406649. The reversal of 406640 is 46604.

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 (20).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 406640.

It is not an unprimeable number, because it can be changed into a prime (406649) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17669 + ... + 17691.

2⁴⁰⁶⁶⁴⁰ is an apocalyptic number.

406640 is a gapful number since it is divisible by the number (40) 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 406640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (562464).

406640 is an abundant number, since it is smaller than the sum of its proper divisors (718288).

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

406640 is a wasteful number, since it uses less digits than its factorization.

406640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66 (or 60 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 406640 is about 637.6833069793. The cubic root of 406640 is about 74.0860940988.

The spelling of 406640 in words is "four hundred six thousand, six hundred forty".