18493721 has 4 divisors (see below), whose sum is σ = 18502452. Its totient is φ = 18484992.

The previous prime is 18493697. The next prime is 18493723. The reversal of 18493721 is 12739481.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 132496 + 18361225 = 364^2 + 4285^2 .

It is a cyclic number.

It is not a de Polignac number, because 18493721 - 2¹⁰ = 18492697 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 (18493723) 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, 1061 + ... + 6173.

It is an arithmetic number, because the mean of its divisors is an integer number (4625613).

Almost surely, 2^18493721 is an apocalyptic number.

It is an amenable number.

18493721 is a deficient number, since it is larger than the sum of its proper divisors (8731).

18493721 is an equidigital number, since it uses as much as digits as its factorization.

18493721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8730.

The product of its digits is 12096, while the sum is 35.

The square root of 18493721 is about 4300.4326526525. The cubic root of 18493721 is about 264.4486984240.

It can be divided in two parts, 1849 and 3721, that multiplied together give a square (6880129 = 2623²).

The spelling of 18493721 in words is "eighteen million, four hundred ninety-three thousand, seven hundred twenty-one".