1215142561 has 4 divisors (see below), whose sum is σ = 1216938132. Its totient is φ = 1213346992.

The previous prime is 1215142499. The next prime is 1215142589. The reversal of 1215142561 is 1652415121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1652415121 = 7 ⋅236059303.

It can be written as a sum of positive squares in 2 ways, for example, as 834112161 + 381030400 = 28881^2 + 19520^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1215142561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1215142261) 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, 896770 + ... + 898123.

It is an arithmetic number, because the mean of its divisors is an integer number (304234533).

Almost surely, 2^1215142561 is an apocalyptic number.

It is an amenable number.

1215142561 is a deficient number, since it is larger than the sum of its proper divisors (1795571).

1215142561 is an equidigital number, since it uses as much as digits as its factorization.

1215142561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1795570.

The product of its digits is 2400, while the sum is 28.

The square root of 1215142561 is about 34858.8950054358. The cubic root of 1215142561 is about 1067.1097242224.

Adding to 1215142561 its reverse (1652415121), we get a palindrome (2867557682).

The spelling of 1215142561 in words is "one billion, two hundred fifteen million, one hundred forty-two thousand, five hundred sixty-one".