18664977649 has 2 divisors, whose sum is σ = 18664977650. Its totient is φ = 18664977648.

The previous prime is 18664977647. The next prime is 18664977691. The reversal of 18664977649 is 94677946681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18531921424 + 133056225 = 136132^2 + 11535^2 .

It is an emirp because it is prime and its reverse (94677946681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18664977649 - 2¹ = 18664977647 is a prime.

Together with 18664977647, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (18664977647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9332488824 + 9332488825.

It is an arithmetic number, because the mean of its divisors is an integer number (9332488825).

Almost surely, 2^18664977649 is an apocalyptic number.

It is an amenable number.

18664977649 is a deficient number, since it is larger than the sum of its proper divisors (1).

18664977649 is an equidigital number, since it uses as much as digits as its factorization.

18664977649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 109734912, while the sum is 67.

The spelling of 18664977649 in words is "eighteen billion, six hundred sixty-four million, nine hundred seventy-seven thousand, six hundred forty-nine".