18067721 has 6 divisors (see below), whose sum is σ = 21017610. Its totient is φ = 15486576.

The previous prime is 18067711. The next prime is 18067739. The reversal of 18067721 is 12776081.

It can be written as a sum of positive squares in only one way, i.e., 17935225 + 132496 = 4235^2 + 364^2 .

It is not a de Polignac number, because 18067721 - 2¹⁸ = 17805577 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18067711) 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, 184316 + ... + 184413.

It is an arithmetic number, because the mean of its divisors is an integer number (3502935).

Almost surely, 2^18067721 is an apocalyptic number.

It is an amenable number.

18067721 is a deficient number, since it is larger than the sum of its proper divisors (2949889).

18067721 is an equidigital number, since it uses as much as digits as its factorization.

18067721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 368743 (or 368736 counting only the distinct ones).

The product of its (nonzero) digits is 4704, while the sum is 32.

The square root of 18067721 is about 4250.6141909141. The cubic root of 18067721 is about 262.4023933406.

The spelling of 18067721 in words is "eighteen million, sixty-seven thousand, seven hundred twenty-one".