18721040 has 80 divisors (see below), whose sum is σ = 47996928. Its totient is φ = 6747648.

The previous prime is 18721033. The next prime is 18721091. The reversal of 18721040 is 4012781.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 18720997 and 18721015.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48689 + ... + 49071.

Almost surely, 2^18721040 is an apocalyptic number.

18721040 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18721040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23998464).

18721040 is an abundant number, since it is smaller than the sum of its proper divisors (29275888).

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

18721040 is a wasteful number, since it uses less digits than its factorization.

18721040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 456 (or 450 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 18721040 is about 4326.7817139301. The cubic root of 18721040 is about 265.5277958516.

The spelling of 18721040 in words is "eighteen million, seven hundred twenty-one thousand, forty".