18130721 has 16 divisors (see below), whose sum is σ = 22106880. Its totient is φ = 14515200.

The previous prime is 18130681. The next prime is 18130727. The reversal of 18130721 is 12703181.

It is a happy number.

It is not a de Polignac number, because 18130721 - 2⁶ = 18130657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18130727) 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, 17465 + ... + 18473.

It is an arithmetic number, because the mean of its divisors is an integer number (1381680).

Almost surely, 2^18130721 is an apocalyptic number.

It is an amenable number.

18130721 is a deficient number, since it is larger than the sum of its proper divisors (3976159).

18130721 is a wasteful number, since it uses less digits than its factorization.

18130721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1184.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 18130721 is about 4258.0184358455. The cubic root of 18130721 is about 262.7070282127.

The spelling of 18130721 in words is "eighteen million, one hundred thirty thousand, seven hundred twenty-one".