18071021 has 4 divisors (see below), whose sum is σ = 18250044. Its totient is φ = 17892000.

The previous prime is 18070999. The next prime is 18071087. The reversal of 18071021 is 12017081.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16080100 + 1990921 = 4010^2 + 1411^2 .

It is a cyclic number.

It is not a de Polignac number, because 18071021 - 2²² = 13876717 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18070984 and 18071002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18071621) 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, 89360 + ... + 89561.

It is an arithmetic number, because the mean of its divisors is an integer number (4562511).

Almost surely, 2^18071021 is an apocalyptic number.

It is an amenable number.

18071021 is a deficient number, since it is larger than the sum of its proper divisors (179023).

18071021 is a wasteful number, since it uses less digits than its factorization.

18071021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179022.

The product of its (nonzero) digits is 112, while the sum is 20.

The square root of 18071021 is about 4251.0023523870. The cubic root of 18071021 is about 262.4183679652.

Subtracting from 18071021 its sum of digits (20), we obtain a square (18071001 = 4251²).

The spelling of 18071021 in words is "eighteen million, seventy-one thousand, twenty-one".