18909471661 has 2 divisors, whose sum is σ = 18909471662. Its totient is φ = 18909471660.

The previous prime is 18909471611. The next prime is 18909471709. The reversal of 18909471661 is 16617490981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18087560100 + 821911561 = 134490^2 + 28669^2 .

It is a cyclic number.

It is not a de Polignac number, because 18909471661 - 2¹⁹ = 18908947373 is a prime.

It is a super-3 number, since 3×18909471661³ (a number of 32 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 18909471599 and 18909471608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18909471611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9454735830 + 9454735831.

It is an arithmetic number, because the mean of its divisors is an integer number (9454735831).

Almost surely, 2^18909471661 is an apocalyptic number.

It is an amenable number.

18909471661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18909471661 is an equidigital number, since it uses as much as digits as its factorization.

18909471661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 653184, while the sum is 52.

The spelling of 18909471661 in words is "eighteen billion, nine hundred nine million, four hundred seventy-one thousand, six hundred sixty-one".