251961840 has 240 divisors, whose sum is σ = 945960288. Its totient is φ = 61959168.

The previous prime is 251961839. The next prime is 251961847. The reversal of 251961840 is 48169152.

251961840 is a `hidden beast` number, since 2 + 519 + 61 + 84 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 251961795 and 251961804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251961847) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 252222 + ... + 253218.

Almost surely, 2^251961840 is an apocalyptic number.

251961840 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 251961840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (472980144).

251961840 is an abundant number, since it is smaller than the sum of its proper divisors (693998448).

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

251961840 is a wasteful number, since it uses less digits than its factorization.

251961840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1038 (or 1020 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 251961840 is about 15873.3058938584. The cubic root of 251961840 is about 631.6040755792.

The spelling of 251961840 in words is "two hundred fifty-one million, nine hundred sixty-one thousand, eight hundred forty".