21415145561 has 2 divisors, whose sum is σ = 21415145562. Its totient is φ = 21415145560.

The previous prime is 21415145491. The next prime is 21415145569. The reversal of 21415145561 is 16554151412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16739184400 + 4675961161 = 129380^2 + 68381^2 .

It is a cyclic number.

It is not a de Polignac number, because 21415145561 - 2¹⁸ = 21414883417 is a prime.

It is not a weakly prime, because it can be changed into another prime (21415145569) 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 as a sum of consecutive naturals, namely, 10707572780 + 10707572781.

It is an arithmetic number, because the mean of its divisors is an integer number (10707572781).

Almost surely, 2^21415145561 is an apocalyptic number.

It is an amenable number.

21415145561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21415145561 is an equidigital number, since it uses as much as digits as its factorization.

21415145561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24000, while the sum is 35.

Adding to 21415145561 its reverse (16554151412), we get a palindrome (37969296973).

The spelling of 21415145561 in words is "twenty-one billion, four hundred fifteen million, one hundred forty-five thousand, five hundred sixty-one".