21530440 has 32 divisors (see below), whose sum is σ = 48692160. Its totient is φ = 8568000.

The previous prime is 21530413. The next prime is 21530447. The reversal of 21530440 is 4403512.

It is not an unprimeable number, because it can be changed into a prime (21530447) 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, 7165 + ... + 9715.

It is an arithmetic number, because the mean of its divisors is an integer number (1521630).

Almost surely, 2^21530440 is an apocalyptic number.

21530440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21530440 is an abundant number, since it is smaller than the sum of its proper divisors (27161720).

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

21530440 is a wasteful number, since it uses less digits than its factorization.

21530440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2773 (or 2769 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21530440 is about 4640.0905163585. The cubic root of 21530440 is about 278.1960558256.

Adding to 21530440 its reverse (4403512), we get a palindrome (25933952).

The spelling of 21530440 in words is "twenty-one million, five hundred thirty thousand, four hundred forty".