251938640 has 80 divisors (see below), whose sum is σ = 623330640. Its totient is φ = 94699520.

The previous prime is 251938637. The next prime is 251938679. The reversal of 251938640 is 46839152.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 11316496 + 240622144 = 3364^2 + 15512^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 251938594 and 251938603.

It is a congruent number.

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, 392720 + ... + 393360.

It is an arithmetic number, because the mean of its divisors is an integer number (7791633).

Almost surely, 2^251938640 is an apocalyptic number.

251938640 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 251938640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (311665320).

251938640 is an abundant number, since it is smaller than the sum of its proper divisors (371392000).

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

251938640 is an equidigital number, since it uses as much as digits as its factorization.

251938640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 705 (or 665 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 38.

The square root of 251938640 is about 15872.5750903878. The cubic root of 251938640 is about 631.5846894897.

It can be divided in two parts, 25193 and 8640, that added together give a palindrome (33833).

The spelling of 251938640 in words is "two hundred fifty-one million, nine hundred thirty-eight thousand, six hundred forty".