21320240 has 40 divisors (see below), whose sum is σ = 50420880. Its totient is φ = 8381696.

The previous prime is 21320239. The next prime is 21320267. The reversal of 21320240 is 4202312.

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

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2462 + ... + 6978.

It is an arithmetic number, because the mean of its divisors is an integer number (1260522).

Almost surely, 2^21320240 is an apocalyptic number.

21320240 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 21320240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25210440).

21320240 is an abundant number, since it is smaller than the sum of its proper divisors (29100640).

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

21320240 is a wasteful number, since it uses less digits than its factorization.

21320240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4589 (or 4583 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 21320240 is about 4617.3845410578. The cubic root of 21320240 is about 277.2877580639.

Adding to 21320240 its reverse (4202312), we get a palindrome (25522552).

The spelling of 21320240 in words is "twenty-one million, three hundred twenty thousand, two hundred forty".