18921816 has 64 divisors (see below), whose sum is σ = 55663200. Its totient is φ = 5935104.

The previous prime is 18921781. The next prime is 18921817. The reversal of 18921816 is 61812981.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18921817) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1096 + ... + 6248.

Almost surely, 2^18921816 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18921816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27831600).

18921816 is an abundant number, since it is smaller than the sum of its proper divisors (36741384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18921816 is a wasteful number, since it uses less digits than its factorization.

18921816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5185 (or 5175 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 18921816 is about 4349.9213785998. The cubic root of 18921816 is about 266.4736506045.

The spelling of 18921816 in words is "eighteen million, nine hundred twenty-one thousand, eight hundred sixteen".