18017571821 has 2 divisors, whose sum is σ = 18017571822. Its totient is φ = 18017571820.

The previous prime is 18017571797. The next prime is 18017571827. The reversal of 18017571821 is 12817571081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10447701796 + 7569870025 = 102214^2 + 87005^2 .

It is a cyclic number.

It is not a de Polignac number, because 18017571821 - 2⁶ = 18017571757 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18017571827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9008785910 + 9008785911.

It is an arithmetic number, because the mean of its divisors is an integer number (9008785911).

Almost surely, 2^18017571821 is an apocalyptic number.

It is an amenable number.

18017571821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18017571821 is an equidigital number, since it uses as much as digits as its factorization.

18017571821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31360, while the sum is 41.

The spelling of 18017571821 in words is "eighteen billion, seventeen million, five hundred seventy-one thousand, eight hundred twenty-one".