251840 has 28 divisors (see below), whose sum is σ = 600456. Its totient is φ = 100608.

The previous prime is 251833. The next prime is 251843. The reversal of 251840 is 48152.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251843) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 74 + ... + 713.

2²⁵¹⁸⁴⁰ is an apocalyptic number.

251840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

251840 is an abundant number, since it is smaller than the sum of its proper divisors (348616).

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

251840 is an equidigital number, since it uses as much as digits as its factorization.

251840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 804 (or 794 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 251840 is about 501.8366268020. The cubic root of 251840 is about 63.1502251895.

251840 divided by its product of nonzero digits (320) gives a palindrome (787).

Adding to 251840 its reverse (48152), we get a palindrome (299992).

The spelling of 251840 in words is "two hundred fifty-one thousand, eight hundred forty".