251531540 has 24 divisors (see below), whose sum is σ = 568848840. Its totient is φ = 92873088.

The previous prime is 251531531. The next prime is 251531563. The reversal of 251531540 is 45135152.

251531540 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 2775556 + 248755984 = 1666^2 + 15772^2 .

It is a super-2 number, since 2×251531540² = 126536231229543200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 483455 + ... + 483974.

It is an arithmetic number, because the mean of its divisors is an integer number (23702035).

Almost surely, 2^251531540 is an apocalyptic number.

251531540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

251531540 is an abundant number, since it is smaller than the sum of its proper divisors (317317300).

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

251531540 is a wasteful number, since it uses less digits than its factorization.

251531540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 967451 (or 967449 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 26.

The square root of 251531540 is about 15859.7458996038. The cubic root of 251531540 is about 631.2443199175.

Adding to 251531540 its reverse (45135152), we get a palindrome (296666692).

The spelling of 251531540 in words is "two hundred fifty-one million, five hundred thirty-one thousand, five hundred forty".