16561440 has 288 divisors, whose sum is σ = 67931136. Its totient is φ = 3594240.

The previous prime is 16561423. The next prime is 16561469. The reversal of 16561440 is 4416561.

16561440 = 106² + 107² + ... + 370².

16561440 is a `hidden beast` number, since 1 + 6 + 5 + 614 + 40 = 666.

16561440 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (288).

It is a nialpdrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 312454 + ... + 312506.

It is an arithmetic number, because the mean of its divisors is an integer number (235872).

Almost surely, 2^16561440 is an apocalyptic number.

16561440 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 16561440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33965568).

16561440 is an abundant number, since it is smaller than the sum of its proper divisors (51369696).

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

16561440 is a wasteful number, since it uses less digits than its factorization.

16561440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112 (or 101 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 16561440 is about 4069.5749163764. The cubic root of 16561440 is about 254.8977675545.

The spelling of 16561440 in words is "sixteen million, five hundred sixty-one thousand, four hundred forty".