18745561 has 2 divisors, whose sum is σ = 18745562. Its totient is φ = 18745560.

The previous prime is 18745537. The next prime is 18745567. The reversal of 18745561 is 16554781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18113536 + 632025 = 4256^2 + 795^2 .

It is a cyclic number.

It is not a de Polignac number, because 18745561 - 2¹¹ = 18743513 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18745561.

It is not a weakly prime, because it can be changed into another prime (18745567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9372780 + 9372781.

It is an arithmetic number, because the mean of its divisors is an integer number (9372781).

Almost surely, 2^18745561 is an apocalyptic number.

It is an amenable number.

18745561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18745561 is an equidigital number, since it uses as much as digits as its factorization.

18745561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 33600, while the sum is 37.

The square root of 18745561 is about 4329.6144170122. The cubic root of 18745561 is about 265.6436755681.

It can be divided in two parts, 18745 and 561, that added together give a triangular number (19306 = T₁₉₆).

The spelling of 18745561 in words is "eighteen million, seven hundred forty-five thousand, five hundred sixty-one".