18520921 has 2 divisors, whose sum is σ = 18520922. Its totient is φ = 18520920.

The previous prime is 18520913. The next prime is 18520933. The reversal of 18520921 is 12902581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18147600 + 373321 = 4260^2 + 611^2 .

It is a cyclic number.

It is not a de Polignac number, because 18520921 - 2³ = 18520913 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18520921.

It is not a weakly prime, because it can be changed into another prime (18520321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9260460 + 9260461.

It is an arithmetic number, because the mean of its divisors is an integer number (9260461).

Almost surely, 2^18520921 is an apocalyptic number.

It is an amenable number.

18520921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18520921 is an equidigital number, since it uses as much as digits as its factorization.

18520921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 18520921 is about 4303.5939631894. The cubic root of 18520921 is about 264.5782826049.

The spelling of 18520921 in words is "eighteen million, five hundred twenty thousand, nine hundred twenty-one".