18613561 has 2 divisors, whose sum is σ = 18613562. Its totient is φ = 18613560.

The previous prime is 18613541. The next prime is 18613577. The reversal of 18613561 is 16531681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11431161 + 7182400 = 3381^2 + 2680^2 .

It is a cyclic number.

It is not a de Polignac number, because 18613561 - 2⁷ = 18613433 is a prime.

It is not a weakly prime, because it can be changed into another prime (18613541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9306780 + 9306781.

It is an arithmetic number, because the mean of its divisors is an integer number (9306781).

Almost surely, 2^18613561 is an apocalyptic number.

It is an amenable number.

18613561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18613561 is an equidigital number, since it uses as much as digits as its factorization.

18613561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 31.

The square root of 18613561 is about 4314.3436348998. The cubic root of 18613561 is about 265.0186814883.

The spelling of 18613561 in words is "eighteen million, six hundred thirteen thousand, five hundred sixty-one".