18406720 has 56 divisors (see below), whose sum is σ = 44357544. Its totient is φ = 7274496.

The previous prime is 18406711. The next prime is 18406727. The reversal of 18406720 is 2760481.

18406720 = T₃₃₅ + T₃₃₆ + ... + T₅₂₈.

It can be written as a sum of positive squares in 4 ways, for example, as 2214144 + 16192576 = 1488^2 + 4024^2 .

It is a super-3 number, since 3×18406720³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18406727) 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, 30744 + ... + 31336.

It is an arithmetic number, because the mean of its divisors is an integer number (792099).

Almost surely, 2^18406720 is an apocalyptic number.

18406720 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 18406720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22178772).

18406720 is an abundant number, since it is smaller than the sum of its proper divisors (25950824).

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

18406720 is an equidigital number, since it uses as much as digits as its factorization.

18406720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 707 (or 697 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 18406720 is about 4290.3053504384. The cubic root of 18406720 is about 264.0333597269.

The spelling of 18406720 in words is "eighteen million, four hundred six thousand, seven hundred twenty".