251315640 has 144 divisors (see below), whose sum is σ = 834439320. Its totient is φ = 65594880.

The previous prime is 251315629. The next prime is 251315657. The reversal of 251315640 is 46513152.

251315640 is a `hidden beast` number, since 2 + 5 + 1 + 3 + 15 + 640 = 666.

251315640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1918375 + ... + 1918505.

Almost surely, 2^251315640 is an apocalyptic number.

251315640 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 251315640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (417219660).

251315640 is an abundant number, since it is smaller than the sum of its proper divisors (583123680).

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

251315640 is a wasteful number, since it uses less digits than its factorization.

251315640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294 (or 214 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 251315640 is about 15852.9378980680. The cubic root of 251315640 is about 631.0636604523.

Adding to 251315640 its reverse (46513152), we get a palindrome (297828792).

The spelling of 251315640 in words is "two hundred fifty-one million, three hundred fifteen thousand, six hundred forty".