18005561280 has 672 divisors, whose sum is σ = 77308008960. Its totient is φ = 3896709120.

The previous prime is 18005561251. The next prime is 18005561281. The reversal of 18005561280 is 8216550081.

18005561280 is a `hidden beast` number, since 1 + 80 + 0 + 556 + 1 + 28 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (672).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18005561281) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 10341210 + ... + 10342950.

It is an arithmetic number, because the mean of its divisors is an integer number (115041680).

Almost surely, 2^18005561280 is an apocalyptic number.

18005561280 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 18005561280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38654004480).

18005561280 is an abundant number, since it is smaller than the sum of its proper divisors (59302447680).

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

18005561280 is a wasteful number, since it uses less digits than its factorization.

18005561280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1799 (or 1777 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 36.

The spelling of 18005561280 in words is "eighteen billion, five million, five hundred sixty-one thousand, two hundred eighty".