72004561 has 2 divisors, whose sum is σ = 72004562. Its totient is φ = 72004560.

The previous prime is 72004549. The next prime is 72004567. The reversal of 72004561 is 16540027.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64496961 + 7507600 = 8031^2 + 2740^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72004561 is a prime.

It is not a weakly prime, because it can be changed into another prime (72004567) 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, 36002280 + 36002281.

It is an arithmetic number, because the mean of its divisors is an integer number (36002281).

Almost surely, 2^72004561 is an apocalyptic number.

It is an amenable number.

72004561 is a deficient number, since it is larger than the sum of its proper divisors (1).

72004561 is an equidigital number, since it uses as much as digits as its factorization.

72004561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 72004561 is about 8485.5501294848. The cubic root of 72004561 is about 416.0255489270.

Adding to 72004561 its reverse (16540027), we get a palindrome (88544588).

The spelling of 72004561 in words is "seventy-two million, four thousand, five hundred sixty-one".