21599440 has 40 divisors (see below), whose sum is σ = 50699880. Its totient is φ = 8557056.

The previous prime is 21599419. The next prime is 21599443. The reversal of 21599440 is 4499512.

It can be written as a sum of positive squares in 4 ways, for example, as 3655744 + 17943696 = 1912^2 + 4236^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 21599396 and 21599405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21599443) 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, 7482 + ... + 9958.

It is an arithmetic number, because the mean of its divisors is an integer number (1267497).

Almost surely, 2^21599440 is an apocalyptic number.

21599440 is a gapful number since it is divisible by the number (20) 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 21599440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25349940).

21599440 is an abundant number, since it is smaller than the sum of its proper divisors (29100440).

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

21599440 is a wasteful number, since it uses less digits than its factorization.

21599440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2599 (or 2593 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 21599440 is about 4647.5197686508. The cubic root of 21599440 is about 278.4929232462.

The spelling of 21599440 in words is "twenty-one million, five hundred ninety-nine thousand, four hundred forty".