251608640 has 112 divisors (see below), whose sum is σ = 652881600. Its totient is φ = 91994112.

The previous prime is 251608633. The next prime is 251608663. The reversal of 251608640 is 46806152.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 251608597 and 251608606.

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 15 ways as a sum of consecutive naturals, for example, 175607 + ... + 177033.

It is an arithmetic number, because the mean of its divisors is an integer number (5829300).

Almost surely, 2^251608640 is an apocalyptic number.

251608640 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 251608640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (326440800).

251608640 is an abundant number, since it is smaller than the sum of its proper divisors (401272960).

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

251608640 is a wasteful number, since it uses less digits than its factorization.

251608640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1492 (or 1482 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 251608640 is about 15862.1763954383. The cubic root of 251608640 is about 631.3088101271.

The spelling of 251608640 in words is "two hundred fifty-one million, six hundred eight thousand, six hundred forty".