251888640 has 264 divisors, whose sum is σ = 869369088. Its totient is φ = 62177280.

The previous prime is 251888633. The next prime is 251888653. The reversal of 251888640 is 46888152.

It is a Cunningham number, because it is equal to 15871²-1.

It is a super-2 number, since 2×251888640² = 126895773922099200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 251888592 and 251888601.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8125425 + ... + 8125455.

Almost surely, 2^251888640 is an apocalyptic number.

251888640 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 251888640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (434684544).

251888640 is an abundant number, since it is smaller than the sum of its proper divisors (617480448).

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

251888640 is a wasteful number, since it uses less digits than its factorization.

251888640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105 (or 64 counting only the distinct ones).

The product of its (nonzero) digits is 122880, while the sum is 42.

The square root of 251888640 is about 15870.9999684960. Note that the first 4 decimals coincide. The cubic root of 251888640 is about 631.5429050777.

The spelling of 251888640 in words is "two hundred fifty-one million, eight hundred eighty-eight thousand, six hundred forty".