18656694821 has 2 divisors, whose sum is σ = 18656694822. Its totient is φ = 18656694820.

The previous prime is 18656694809. The next prime is 18656694827. The reversal of 18656694821 is 12849665681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13886029921 + 4770664900 = 117839^2 + 69070^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18656694821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18656694827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9328347410 + 9328347411.

It is an arithmetic number, because the mean of its divisors is an integer number (9328347411).

Almost surely, 2^18656694821 is an apocalyptic number.

It is an amenable number.

18656694821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18656694821 is an equidigital number, since it uses as much as digits as its factorization.

18656694821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4976640, while the sum is 56.

The spelling of 18656694821 in words is "eighteen billion, six hundred fifty-six million, six hundred ninety-four thousand, eight hundred twenty-one".