18988921 has 6 divisors (see below), whose sum is σ = 22089210. Its totient is φ = 16276176.

The previous prime is 18988919. The next prime is 18988927. The reversal of 18988921 is 12988981.

It can be written as a sum of positive squares in only one way, i.e., 11148921 + 7840000 = 3339^2 + 2800^2 .

It is not a de Polignac number, because 18988921 - 2¹ = 18988919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18988927) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 193716 + ... + 193813.

It is an arithmetic number, because the mean of its divisors is an integer number (3681535).

Almost surely, 2^18988921 is an apocalyptic number.

It is an amenable number.

18988921 is a deficient number, since it is larger than the sum of its proper divisors (3100289).

18988921 is an equidigital number, since it uses as much as digits as its factorization.

18988921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 387543 (or 387536 counting only the distinct ones).

The product of its digits is 82944, while the sum is 46.

The square root of 18988921 is about 4357.6279097693. The cubic root of 18988921 is about 266.7882894864.

The spelling of 18988921 in words is "eighteen million, nine hundred eighty-eight thousand, nine hundred twenty-one".