18671721 has 8 divisors (see below), whose sum is σ = 25236960. Its totient is φ = 12277152.

The previous prime is 18671713. The next prime is 18671743. The reversal of 18671721 is 12717681.

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

It is not a de Polignac number, because 18671721 - 2³ = 18671713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18671701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 42411 + ... + 42848.

It is an arithmetic number, because the mean of its divisors is an integer number (3154620).

Almost surely, 2^18671721 is an apocalyptic number.

It is an amenable number.

18671721 is a deficient number, since it is larger than the sum of its proper divisors (6565239).

18671721 is an equidigital number, since it uses as much as digits as its factorization.

18671721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85335.

The product of its digits is 4704, while the sum is 33.

The square root of 18671721 is about 4321.0786847731. The cubic root of 18671721 is about 265.2944206057.

The spelling of 18671721 in words is "eighteen million, six hundred seventy-one thousand, seven hundred twenty-one".