18968561 has 2 divisors, whose sum is σ = 18968562. Its totient is φ = 18968560.

The previous prime is 18968513. The next prime is 18968567. The reversal of 18968561 is 16586981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15358561 + 3610000 = 3919^2 + 1900^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18968561 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18968567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9484280 + 9484281.

It is an arithmetic number, because the mean of its divisors is an integer number (9484281).

Almost surely, 2^18968561 is an apocalyptic number.

It is an amenable number.

18968561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18968561 is an equidigital number, since it uses as much as digits as its factorization.

18968561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 44.

The square root of 18968561 is about 4355.2911498544. The cubic root of 18968561 is about 266.6929048835.

The spelling of 18968561 in words is "eighteen million, nine hundred sixty-eight thousand, five hundred sixty-one".