251720 has 64 divisors (see below), whose sum is σ = 691200. Its totient is φ = 80640.

The previous prime is 251707. The next prime is 251737. The reversal of 251720 is 27152.

It is an Ulam number.

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 251720.

It is an unprimeable number.

251720 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8105 + ... + 8135.

It is an arithmetic number, because the mean of its divisors is an integer number (10800).

2²⁵¹⁷²⁰ is an apocalyptic number.

251720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

251720 is the 290-th octagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 251720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (345600).

251720 is an abundant number, since it is smaller than the sum of its proper divisors (439480).

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

251720 is a wasteful number, since it uses less digits than its factorization.

251720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78 (or 74 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 251720 is about 501.7170517333. The cubic root of 251720 is about 63.1401933824.

Adding to 251720 its reverse (27152), we get a palindrome (278872).

The spelling of 251720 in words is "two hundred fifty-one thousand, seven hundred twenty".