18101561 has 2 divisors, whose sum is σ = 18101562. Its totient is φ = 18101560.

The previous prime is 18101557. The next prime is 18101593. The reversal of 18101561 is 16510181.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12250000 + 5851561 = 3500^2 + 2419^2 .

It is an emirp because it is prime and its reverse (16510181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18101561 - 2² = 18101557 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18101761) 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, 9050780 + 9050781.

It is an arithmetic number, because the mean of its divisors is an integer number (9050781).

Almost surely, 2^18101561 is an apocalyptic number.

It is an amenable number.

18101561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18101561 is an equidigital number, since it uses as much as digits as its factorization.

18101561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 240, while the sum is 23.

The square root of 18101561 is about 4254.5929299993. The cubic root of 18101561 is about 262.5661136570.

The spelling of 18101561 in words is "eighteen million, one hundred one thousand, five hundred sixty-one".