251817940 has 72 divisors (see below), whose sum is σ = 615554856. Its totient is φ = 86169600.

The previous prime is 251817931. The next prime is 251817949. The reversal of 251817940 is 49718152.

It is an interprime number because it is at equal distance from previous prime (251817931) and next prime (251817949).

It can be written as a sum of positive squares in 4 ways, for example, as 15335056 + 236482884 = 3916^2 + 15378^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 251817940.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251817949) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 38080 + ... + 44200.

It is an arithmetic number, because the mean of its divisors is an integer number (8549373).

Almost surely, 2^251817940 is an apocalyptic number.

251817940 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 251817940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (307777428).

251817940 is an abundant number, since it is smaller than the sum of its proper divisors (363736916).

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

251817940 is a wasteful number, since it uses less digits than its factorization.

251817940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6169 (or 6156 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 37.

The square root of 251817940 is about 15868.7724793066. The cubic root of 251817940 is about 631.4838124810.

The spelling of 251817940 in words is "two hundred fifty-one million, eight hundred seventeen thousand, nine hundred forty".