1265204561 has 4 divisors (see below), whose sum is σ = 1265286000. Its totient is φ = 1265123124.

The previous prime is 1265204543. The next prime is 1265204569. The reversal of 1265204561 is 1654025621.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1265204561 - 2⁶ = 1265204497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1265204569) 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 3 ways as a sum of consecutive naturals, for example, 9371 + ... + 51168.

It is an arithmetic number, because the mean of its divisors is an integer number (316321500).

Almost surely, 2^1265204561 is an apocalyptic number.

It is an amenable number.

1265204561 is a deficient number, since it is larger than the sum of its proper divisors (81439).

1265204561 is an equidigital number, since it uses as much as digits as its factorization.

1265204561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81438.

The product of its (nonzero) digits is 14400, while the sum is 32.

The square root of 1265204561 is about 35569.7140978108. The cubic root of 1265204561 is about 1081.5673861008.

The spelling of 1265204561 in words is "one billion, two hundred sixty-five million, two hundred four thousand, five hundred sixty-one".