18721730 has 8 divisors (see below), whose sum is σ = 33699132. Its totient is φ = 7488688.

The previous prime is 18721723. The next prime is 18721739. The reversal of 18721730 is 3712781.

It can be written as a sum of positive squares in 2 ways, for example, as 15062161 + 3659569 = 3881^2 + 1913^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 18721693 and 18721702.

It is not an unprimeable number, because it can be changed into a prime (18721739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 936077 + ... + 936096.

Almost surely, 2^18721730 is an apocalyptic number.

18721730 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

18721730 is a deficient number, since it is larger than the sum of its proper divisors (14977402).

18721730 is a wasteful number, since it uses less digits than its factorization.

18721730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1872180.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 18721730 is about 4326.8614491338. The cubic root of 18721730 is about 265.5310579911.

The spelling of 18721730 in words is "eighteen million, seven hundred twenty-one thousand, seven hundred thirty".