18922781 has 2 divisors, whose sum is σ = 18922782. Its totient is φ = 18922780.

The previous prime is 18922777. The next prime is 18922793. The reversal of 18922781 is 18722981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18705625 + 217156 = 4325^2 + 466^2 .

It is an emirp because it is prime and its reverse (18722981) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18922781 - 2² = 18922777 is a prime.

It is a super-2 number, since 2×18922781² = 716143281547922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18921781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9461390 + 9461391.

It is an arithmetic number, because the mean of its divisors is an integer number (9461391).

Almost surely, 2^18922781 is an apocalyptic number.

It is an amenable number.

18922781 is a deficient number, since it is larger than the sum of its proper divisors (1).

18922781 is an equidigital number, since it uses as much as digits as its factorization.

18922781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16128, while the sum is 38.

The square root of 18922781 is about 4350.0322987307. The cubic root of 18922781 is about 266.4781805203.

The spelling of 18922781 in words is "eighteen million, nine hundred twenty-two thousand, seven hundred eighty-one".