1817768921 has 2 divisors, whose sum is σ = 1817768922. Its totient is φ = 1817768920.

The previous prime is 1817768903. The next prime is 1817768929. The reversal of 1817768921 is 1298677181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1719263296 + 98505625 = 41464^2 + 9925^2 .

It is an emirp because it is prime and its reverse (1298677181) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1817768921 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1817768921.

It is not a weakly prime, because it can be changed into another prime (1817768929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 908884460 + 908884461.

It is an arithmetic number, because the mean of its divisors is an integer number (908884461).

Almost surely, 2^1817768921 is an apocalyptic number.

It is an amenable number.

1817768921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1817768921 is an equidigital number, since it uses as much as digits as its factorization.

1817768921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 338688, while the sum is 50.

The square root of 1817768921 is about 42635.3013475922. The cubic root of 1817768921 is about 1220.4300465914.

The spelling of 1817768921 in words is "one billion, eight hundred seventeen million, seven hundred sixty-eight thousand, nine hundred twenty-one".