1251387665 has 16 divisors (see below), whose sum is σ = 1644114240. Its totient is φ = 906803520.

The previous prime is 1251387661. The next prime is 1251387707. The reversal of 1251387665 is 5667831521.

It is not a de Polignac number, because 1251387665 - 2² = 1251387661 is a prime.

It is a super-2 number, since 2×1251387665² = 3131942176228304450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1251387661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25835 + ... + 56304.

It is an arithmetic number, because the mean of its divisors is an integer number (102757140).

Almost surely, 2^1251387665 is an apocalyptic number.

It is an amenable number.

1251387665 is a deficient number, since it is larger than the sum of its proper divisors (392726575).

1251387665 is a wasteful number, since it uses less digits than its factorization.

1251387665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82432.

The product of its digits is 302400, while the sum is 44.

The square root of 1251387665 is about 35374.9581625194. The cubic root of 1251387665 is about 1077.6158154159.

The spelling of 1251387665 in words is "one billion, two hundred fifty-one million, three hundred eighty-seven thousand, six hundred sixty-five".