18961444321 has 2 divisors, whose sum is σ = 18961444322. Its totient is φ = 18961444320.

The previous prime is 18961444261. The next prime is 18961444331. The reversal of 18961444321 is 12344416981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10673162721 + 8288281600 = 103311^2 + 91040^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18961444321 is a prime.

It is not a weakly prime, because it can be changed into another prime (18961444331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9480722160 + 9480722161.

It is an arithmetic number, because the mean of its divisors is an integer number (9480722161).

Almost surely, 2^18961444321 is an apocalyptic number.

It is an amenable number.

18961444321 is a deficient number, since it is larger than the sum of its proper divisors (1).

18961444321 is an equidigital number, since it uses as much as digits as its factorization.

18961444321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 165888, while the sum is 43.

The spelling of 18961444321 in words is "eighteen billion, nine hundred sixty-one million, four hundred forty-four thousand, three hundred twenty-one".