251640540 has 96 divisors (see below), whose sum is σ = 809928000. Its totient is φ = 64786176.

The previous prime is 251640533. The next prime is 251640551. The reversal of 251640540 is 45046152.

251640540 is a `hidden beast` number, since 251 + 6 + 405 + 4 + 0 = 666.

It is a super-2 number, since 2×251640540² = 126645922742983200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7626 + ... + 23694.

It is an arithmetic number, because the mean of its divisors is an integer number (8436750).

Almost surely, 2^251640540 is an apocalyptic number.

251640540 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 251640540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (404964000).

251640540 is an abundant number, since it is smaller than the sum of its proper divisors (558287460).

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

251640540 is a wasteful number, since it uses less digits than its factorization.

251640540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16116 (or 16108 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

The square root of 251640540 is about 15863.1819002368. The cubic root of 251640540 is about 631.3354889937.

Adding to 251640540 its reverse (45046152), we get a palindrome (296686692).

The spelling of 251640540 in words is "two hundred fifty-one million, six hundred forty thousand, five hundred forty".