1245561521 has 4 divisors (see below), whose sum is σ = 1274528112. Its totient is φ = 1216594932.

The previous prime is 1245561469. The next prime is 1245561529. The reversal of 1245561521 is 1251655421.

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 an emirpimes, since its reverse is a distinct semiprime: 1251655421 = 41 ⋅30528181.

It is a cyclic number.

It is not a de Polignac number, because 1245561521 - 2²⁶ = 1178452657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1245561529) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14483231 + ... + 14483316.

It is an arithmetic number, because the mean of its divisors is an integer number (318632028).

Almost surely, 2^1245561521 is an apocalyptic number.

It is an amenable number.

1245561521 is a deficient number, since it is larger than the sum of its proper divisors (28966591).

1245561521 is an equidigital number, since it uses as much as digits as its factorization.

1245561521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28966590.

The product of its digits is 12000, while the sum is 32.

The square root of 1245561521 is about 35292.5136679155. The cubic root of 1245561521 is about 1075.9408445457.

The spelling of 1245561521 in words is "one billion, two hundred forty-five million, five hundred sixty-one thousand, five hundred twenty-one".