21131440 has 120 divisors (see below), whose sum is σ = 56402640. Its totient is φ = 7349760.

The previous prime is 21131423. The next prime is 21131449. The reversal of 21131440 is 4413112.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is not an unprimeable number, because it can be changed into a prime (21131449) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 358131 + ... + 358189.

It is an arithmetic number, because the mean of its divisors is an integer number (470022).

Almost surely, 2^21131440 is an apocalyptic number.

21131440 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 21131440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28201320).

21131440 is an abundant number, since it is smaller than the sum of its proper divisors (35271200).

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

21131440 is a wasteful number, since it uses less digits than its factorization.

21131440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131 (or 114 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 21131440 is about 4596.8946039691. The cubic root of 21131440 is about 276.4668288041.

Adding to 21131440 its reverse (4413112), we get a palindrome (25544552).

It can be divided in two parts, 2113 and 1440, that added together give a palindrome (3553).

The spelling of 21131440 in words is "twenty-one million, one hundred thirty-one thousand, four hundred forty".