18808021 has 2 divisors, whose sum is σ = 18808022. Its totient is φ = 18808020.

The previous prime is 18808007. The next prime is 18808033. The reversal of 18808021 is 12080881.

It is the 1771-st star number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18190225 + 617796 = 4265^2 + 786^2 .

It is a cyclic number.

It is not a de Polignac number, because 18808021 - 2⁵ = 18807989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18808051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9404010 + 9404011.

It is an arithmetic number, because the mean of its divisors is an integer number (9404011).

Almost surely, 2^18808021 is an apocalyptic number.

It is an amenable number.

18808021 is a deficient number, since it is larger than the sum of its proper divisors (1).

18808021 is an equidigital number, since it uses as much as digits as its factorization.

18808021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1024, while the sum is 28.

The square root of 18808021 is about 4336.8215319517. The cubic root of 18808021 is about 265.9383890700.

The spelling of 18808021 in words is "eighteen million, eight hundred eight thousand, twenty-one".