18890021 has 2 divisors, whose sum is σ = 18890022. Its totient is φ = 18890020.

The previous prime is 18889999. The next prime is 18890033. The reversal of 18890021 is 12009881.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18105025 + 784996 = 4255^2 + 886^2 .

It is a cyclic number.

It is not a de Polignac number, because 18890021 - 2⁶ = 18889957 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18899021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9445010 + 9445011.

It is an arithmetic number, because the mean of its divisors is an integer number (9445011).

Almost surely, 2^18890021 is an apocalyptic number.

It is an amenable number.

18890021 is a deficient number, since it is larger than the sum of its proper divisors (1).

18890021 is an equidigital number, since it uses as much as digits as its factorization.

18890021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 18890021 is about 4346.2651782881. The cubic root of 18890021 is about 266.3243118779.

It can be divided in two parts, 188 and 90021, that added together give a palindrome (90209).

The spelling of 18890021 in words is "eighteen million, eight hundred ninety thousand, twenty-one".