18740021 has 2 divisors, whose sum is σ = 18740022. Its totient is φ = 18740020.

The previous prime is 18740017. The next prime is 18740053. The reversal of 18740021 is 12004781.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12859396 + 5880625 = 3586^2 + 2425^2 .

It is a cyclic number.

It is not a de Polignac number, because 18740021 - 2² = 18740017 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18740081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9370010 + 9370011.

It is an arithmetic number, because the mean of its divisors is an integer number (9370011).

Almost surely, 2^18740021 is an apocalyptic number.

It is an amenable number.

18740021 is a deficient number, since it is larger than the sum of its proper divisors (1).

18740021 is an equidigital number, since it uses as much as digits as its factorization.

18740021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 18740021 is about 4328.9745899000. The cubic root of 18740021 is about 265.6175038438.

The spelling of 18740021 in words is "eighteen million, seven hundred forty thousand, twenty-one".