18661661 has 2 divisors, whose sum is σ = 18661662. Its totient is φ = 18661660.

The previous prime is 18661639. The next prime is 18661663. The reversal of 18661661 is 16616681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18619225 + 42436 = 4315^2 + 206^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18661661 is a prime.

Together with 18661663, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18661663) 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, 9330830 + 9330831.

It is an arithmetic number, because the mean of its divisors is an integer number (9330831).

Almost surely, 2^18661661 is an apocalyptic number.

It is an amenable number.

18661661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18661661 is an equidigital number, since it uses as much as digits as its factorization.

18661661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 35.

The square root of 18661661 is about 4319.9144667458. The cubic root of 18661661 is about 265.2467666994.

The spelling of 18661661 in words is "eighteen million, six hundred sixty-one thousand, six hundred sixty-one".