18421621 has 4 divisors (see below), whose sum is σ = 19391200. Its totient is φ = 17452044.

The previous prime is 18421619. The next prime is 18421631. The reversal of 18421621 is 12612481.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 18421621 - 2¹ = 18421619 is a prime.

It is a super-2 number, since 2×18421621² = 678712240535282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18421631) 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, 484761 + ... + 484798.

It is an arithmetic number, because the mean of its divisors is an integer number (4847800).

Almost surely, 2^18421621 is an apocalyptic number.

It is an amenable number.

18421621 is a deficient number, since it is larger than the sum of its proper divisors (969579).

18421621 is an equidigital number, since it uses as much as digits as its factorization.

18421621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 969578.

The product of its digits is 768, while the sum is 25.

The square root of 18421621 is about 4292.0415888013. The cubic root of 18421621 is about 264.1045891455.

The spelling of 18421621 in words is "eighteen million, four hundred twenty-one thousand, six hundred twenty-one".