18816421 has 8 divisors (see below), whose sum is σ = 20444760. Its totient is φ = 17213952.

The previous prime is 18816419. The next prime is 18816437. The reversal of 18816421 is 12461881.

It can be written as a sum of positive squares in 4 ways, for example, as 923521 + 17892900 = 961^2 + 4230^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 18816421 - 2¹ = 18816419 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18016421) 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, 4936 + ... + 7873.

It is an arithmetic number, because the mean of its divisors is an integer number (2555595).

Almost surely, 2^18816421 is an apocalyptic number.

It is an amenable number.

18816421 is a deficient number, since it is larger than the sum of its proper divisors (1628339).

18816421 is a wasteful number, since it uses less digits than its factorization.

18816421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12935.

The product of its digits is 3072, while the sum is 31.

The square root of 18816421 is about 4337.7898750401. The cubic root of 18816421 is about 265.9779741311.

The spelling of 18816421 in words is "eighteen million, eight hundred sixteen thousand, four hundred twenty-one".