21006340 has 12 divisors (see below), whose sum is σ = 44113356. Its totient is φ = 8402528.

The previous prime is 21006329. The next prime is 21006341. The reversal of 21006340 is 4360012.

It can be written as a sum of positive squares in 2 ways, for example, as 8714304 + 12292036 = 2952^2 + 3506^2 .

It is not an unprimeable number, because it can be changed into a prime (21006341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 525139 + ... + 525178.

It is an arithmetic number, because the mean of its divisors is an integer number (3676113).

Almost surely, 2^21006340 is an apocalyptic number.

21006340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21006340 is an abundant number, since it is smaller than the sum of its proper divisors (23107016).

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

21006340 is a wasteful number, since it uses less digits than its factorization.

21006340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1050326 (or 1050324 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21006340 is about 4583.2673934651. The cubic root of 21006340 is about 275.9201792561.

Adding to 21006340 its reverse (4360012), we get a palindrome (25366352).

The spelling of 21006340 in words is "twenty-one million, six thousand, three hundred forty".