18394021 has 4 divisors (see below), whose sum is σ = 18741132. Its totient is φ = 18046912.

The previous prime is 18393989. The next prime is 18394073. The reversal of 18394021 is 12049381.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12049381 = 3313 ⋅3637.

It can be written as a sum of positive squares in 2 ways, for example, as 4622500 + 13771521 = 2150^2 + 3711^2 .

It is a cyclic number.

It is not a de Polignac number, because 18394021 - 2⁵ = 18393989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18394121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 173476 + ... + 173581.

It is an arithmetic number, because the mean of its divisors is an integer number (4685283).

Almost surely, 2^18394021 is an apocalyptic number.

It is an amenable number.

18394021 is a deficient number, since it is larger than the sum of its proper divisors (347111).

18394021 is an equidigital number, since it uses as much as digits as its factorization.

18394021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 347110.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 18394021 is about 4288.8251304990. The cubic root of 18394021 is about 263.9726259113.

The spelling of 18394021 in words is "eighteen million, three hundred ninety-four thousand, twenty-one".