18731021 has 2 divisors, whose sum is σ = 18731022. Its totient is φ = 18731020.

The previous prime is 18730981. The next prime is 18731023. The reversal of 18731021 is 12013781.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9796900 + 8934121 = 3130^2 + 2989^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18731021 is a prime.

It is a super-2 number, since 2×18731021² = 701702295404882, which contains 22 as substring.

Together with 18731023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18731023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9365510 + 9365511.

It is an arithmetic number, because the mean of its divisors is an integer number (9365511).

Almost surely, 2^18731021 is an apocalyptic number.

It is an amenable number.

18731021 is a deficient number, since it is larger than the sum of its proper divisors (1).

18731021 is an equidigital number, since it uses as much as digits as its factorization.

18731021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 18731021 is about 4327.9349579216. The cubic root of 18731021 is about 265.5749756039.

The spelling of 18731021 in words is "eighteen million, seven hundred thirty-one thousand, twenty-one".