18940921 has 4 divisors (see below), whose sum is σ = 18994932. Its totient is φ = 18886912.

The previous prime is 18940919. The next prime is 18940931. The reversal of 18940921 is 12904981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12904981 = 3457 ⋅3733.

It can be written as a sum of positive squares in 2 ways, for example, as 11128896 + 7812025 = 3336^2 + 2795^2 .

It is not a de Polignac number, because 18940921 - 2¹ = 18940919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18940931) 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 in 3 ways as a sum of consecutive naturals, for example, 26476 + ... + 27181.

It is an arithmetic number, because the mean of its divisors is an integer number (4748733).

Almost surely, 2^18940921 is an apocalyptic number.

It is an amenable number.

18940921 is a deficient number, since it is larger than the sum of its proper divisors (54011).

18940921 is an equidigital number, since it uses as much as digits as its factorization.

18940921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54010.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 18940921 is about 4352.1168412624. The cubic root of 18940921 is about 266.5633049068.

The spelling of 18940921 in words is "eighteen million, nine hundred forty thousand, nine hundred twenty-one".