12001215521 has 4 divisors (see below), whose sum is σ = 12002105412. Its totient is φ = 12000325632.

The previous prime is 12001215509. The next prime is 12001215533. The reversal of 12001215521 is 12551210021.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12551210021 = 7 ⋅1793030003.

It is an interprime number because it is at equal distance from previous prime (12001215509) and next prime (12001215533).

It can be written as a sum of positive squares in 2 ways, for example, as 5827184896 + 6174030625 = 76336^2 + 78575^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12001215521 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 12001215493 and 12001215502.

It is not an unprimeable number, because it can be changed into a prime (12001215571) 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, 424400 + ... + 451793.

It is an arithmetic number, because the mean of its divisors is an integer number (3000526353).

Almost surely, 2^12001215521 is an apocalyptic number.

It is an amenable number.

12001215521 is a deficient number, since it is larger than the sum of its proper divisors (889891).

12001215521 is an equidigital number, since it uses as much as digits as its factorization.

12001215521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 889890.

The product of its (nonzero) digits is 200, while the sum is 20.

Adding to 12001215521 its reverse (12551210021), we get a palindrome (24552425542).

The spelling of 12001215521 in words is "twelve billion, one million, two hundred fifteen thousand, five hundred twenty-one".