1215545521 has 2 divisors, whose sum is σ = 1215545522. Its totient is φ = 1215545520.

The previous prime is 1215545477. The next prime is 1215545549. The reversal of 1215545521 is 1255455121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1008761121 + 206784400 = 31761^2 + 14380^2 .

It is an emirp because it is prime and its reverse (1255455121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1215545521 - 2⁷ = 1215545393 is a prime.

It is a super-2 number, since 2×1215545521² = 2955101827246322882, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1215545581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 607772760 + 607772761.

It is an arithmetic number, because the mean of its divisors is an integer number (607772761).

Almost surely, 2^1215545521 is an apocalyptic number.

It is an amenable number.

1215545521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1215545521 is an equidigital number, since it uses as much as digits as its factorization.

1215545521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10000, while the sum is 31.

The square root of 1215545521 is about 34864.6743997416. The cubic root of 1215545521 is about 1067.2276678627.

The spelling of 1215545521 in words is "one billion, two hundred fifteen million, five hundred forty-five thousand, five hundred twenty-one".