257640 has 64 divisors (see below), whose sum is σ = 820800. Its totient is φ = 64512.

The previous prime is 257639. The next prime is 257657. The reversal of 257640 is 46752.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 257640.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 257640.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2224 + ... + 2336.

It is an arithmetic number, because the mean of its divisors is an integer number (12825).

2²⁵⁷⁶⁴⁰ is an apocalyptic number.

257640 is a gapful number since it is divisible by the number (20) 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 257640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (410400).

257640 is an abundant number, since it is smaller than the sum of its proper divisors (563160).

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

257640 is a wasteful number, since it uses less digits than its factorization.

257640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 257640 is about 507.5825056087. The cubic root of 257640 is about 63.6313440691.

The spelling of 257640 in words is "two hundred fifty-seven thousand, six hundred forty".