18724821 has 8 divisors (see below), whose sum is σ = 25060320. Its totient is φ = 12436272.

The previous prime is 18724813. The next prime is 18724831. The reversal of 18724821 is 12842781.

It is a happy number.

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

It is not a de Polignac number, because 18724821 - 2³ = 18724813 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18724801) 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, 10795 + ... + 12408.

It is an arithmetic number, because the mean of its divisors is an integer number (3132540).

Almost surely, 2^18724821 is an apocalyptic number.

It is an amenable number.

18724821 is a deficient number, since it is larger than the sum of its proper divisors (6335499).

18724821 is a wasteful number, since it uses less digits than its factorization.

18724821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23475.

The product of its digits is 7168, while the sum is 33.

The square root of 18724821 is about 4327.2186217015. The cubic root of 18724821 is about 265.5456704465.

The spelling of 18724821 in words is "eighteen million, seven hundred twenty-four thousand, eight hundred twenty-one".