21310240 has 96 divisors (see below), whose sum is σ = 58786560. Its totient is φ = 7148544.

The previous prime is 21310207. The next prime is 21310243. The reversal of 21310240 is 4201312.

It is a self number, because there is not a number n which added to its sum of digits gives 21310240.

It is not an unprimeable number, because it can be changed into a prime (21310243) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 59181 + ... + 59539.

It is an arithmetic number, because the mean of its divisors is an integer number (612360).

Almost surely, 2^21310240 is an apocalyptic number.

21310240 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 21310240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29393280).

21310240 is an abundant number, since it is smaller than the sum of its proper divisors (37476320).

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

21310240 is a wasteful number, since it uses less digits than its factorization.

21310240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 434 (or 426 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21310240 is about 4616.3015499423. The cubic root of 21310240 is about 277.2443984641.

Adding to 21310240 its reverse (4201312), we get a palindrome (25511552).

The spelling of 21310240 in words is "twenty-one million, three hundred ten thousand, two hundred forty".