18440645281 has 2 divisors, whose sum is σ = 18440645282. Its totient is φ = 18440645280.

The previous prime is 18440645261. The next prime is 18440645351. The reversal of 18440645281 is 18254604481.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13999622400 + 4441022881 = 118320^2 + 66641^2 .

It is an emirp because it is prime and its reverse (18254604481) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18440645281 is a prime.

It is a super-2 number, since 2×18440645281² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18440645261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9220322640 + 9220322641.

It is an arithmetic number, because the mean of its divisors is an integer number (9220322641).

Almost surely, 2^18440645281 is an apocalyptic number.

It is an amenable number.

18440645281 is a deficient number, since it is larger than the sum of its proper divisors (1).

18440645281 is an equidigital number, since it uses as much as digits as its factorization.

18440645281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 245760, while the sum is 43.

The spelling of 18440645281 in words is "eighteen billion, four hundred forty million, six hundred forty-five thousand, two hundred eighty-one".