1251565540 has 24 divisors (see below), whose sum is σ = 2638069560. Its totient is φ = 498763008.

The previous prime is 1251565537. The next prime is 1251565541. The reversal of 1251565540 is 455651521.

It can be written as a sum of positive squares in 4 ways, for example, as 69856164 + 1181709376 = 8358^2 + 34376^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1251565496 and 1251565505.

It is not an unprimeable number, because it can be changed into a prime (1251565541) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 110937 + ... + 121696.

It is an arithmetic number, because the mean of its divisors is an integer number (109919565).

Almost surely, 2^1251565540 is an apocalyptic number.

1251565540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1251565540 is an abundant number, since it is smaller than the sum of its proper divisors (1386504020).

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

1251565540 is a wasteful number, since it uses less digits than its factorization.

1251565540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232911 (or 232909 counting only the distinct ones).

The product of its (nonzero) digits is 30000, while the sum is 34.

The square root of 1251565540 is about 35377.4722104336. The cubic root of 1251565540 is about 1077.6668712258. Note that the first 3 decimals are identical.

The spelling of 1251565540 in words is "one billion, two hundred fifty-one million, five hundred sixty-five thousand, five hundred forty".