9181664021 has 2 divisors, whose sum is σ = 9181664022. Its totient is φ = 9181664020.

The previous prime is 9181664017. The next prime is 9181664027. The reversal of 9181664021 is 1204661819.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9142036996 + 39627025 = 95614^2 + 6295^2 .

It is an emirp because it is prime and its reverse (1204661819) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9181664021 - 2² = 9181664017 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9181664027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4590832010 + 4590832011.

It is an arithmetic number, because the mean of its divisors is an integer number (4590832011).

Almost surely, 2^9181664021 is an apocalyptic number.

It is an amenable number.

9181664021 is a deficient number, since it is larger than the sum of its proper divisors (1).

9181664021 is an equidigital number, since it uses as much as digits as its factorization.

9181664021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 38.

The square root of 9181664021 is about 95820.9998956387. Note that the first 3 decimals coincide. The cubic root of 9181664021 is about 2093.9861215478.

The spelling of 9181664021 in words is "nine billion, one hundred eighty-one million, six hundred sixty-four thousand, twenty-one".