1265800821 has 16 divisors (see below), whose sum is σ = 1751233344. Its totient is φ = 812588544.

The previous prime is 1265800819. The next prime is 1265800867. The reversal of 1265800821 is 1280085621.

It is not a de Polignac number, because 1265800821 - 2¹ = 1265800819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1265800871) 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 15 ways as a sum of consecutive naturals, for example, 48015 + ... + 69548.

It is an arithmetic number, because the mean of its divisors is an integer number (109452084).

Almost surely, 2^1265800821 is an apocalyptic number.

It is an amenable number.

1265800821 is a deficient number, since it is larger than the sum of its proper divisors (485432523).

1265800821 is a wasteful number, since it uses less digits than its factorization.

1265800821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117700.

The product of its (nonzero) digits is 7680, while the sum is 33.

The square root of 1265800821 is about 35578.0946791702. The cubic root of 1265800821 is about 1081.7372648457.

It can be divided in two parts, 1265800 and 821, that added together give a palindrome (1266621).

The spelling of 1265800821 in words is "one billion, two hundred sixty-five million, eight hundred thousand, eight hundred twenty-one".