1265521221 has 6 divisors (see below), whose sum is σ = 1827975110. Its totient is φ = 843680808.

The previous prime is 1265521217. The next prime is 1265521223. The reversal of 1265521221 is 1221255621.

1265521221 is a `hidden beast` number, since 1 + 2 + 655 + 2 + 1 + 2 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1263802500 + 1718721 = 35550^2 + 1311^2 .

It is not a de Polignac number, because 1265521221 - 2² = 1265521217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1265521223) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 70306726 + ... + 70306743.

Almost surely, 2^1265521221 is an apocalyptic number.

It is an amenable number.

1265521221 is a deficient number, since it is larger than the sum of its proper divisors (562453889).

1265521221 is a wasteful number, since it uses less digits than its factorization.

1265521221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140613475 (or 140613472 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 1265521221 is about 35574.1650780451. The cubic root of 1265521221 is about 1081.6576114472.

Adding to 1265521221 its reverse (1221255621), we get a palindrome (2486776842).

The spelling of 1265521221 in words is "one billion, two hundred sixty-five million, five hundred twenty-one thousand, two hundred twenty-one".