18420021 has 16 divisors (see below), whose sum is σ = 27357120. Its totient is φ = 12249360.

The previous prime is 18420011. The next prime is 18420047. The reversal of 18420021 is 12002481.

It is not a de Polignac number, because 18420021 - 2¹⁸ = 18157877 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 18419976 and 18420003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18420011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16831 + ... + 17891.

It is an arithmetic number, because the mean of its divisors is an integer number (1709820).

Almost surely, 2^18420021 is an apocalyptic number.

It is an amenable number.

18420021 is a deficient number, since it is larger than the sum of its proper divisors (8937099).

18420021 is a wasteful number, since it uses less digits than its factorization.

18420021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1713 (or 1707 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 18420021 is about 4291.8551932702. The cubic root of 18420021 is about 264.0969427034.

The spelling of 18420021 in words is "eighteen million, four hundred twenty thousand, twenty-one".