21013040 has 80 divisors (see below), whose sum is σ = 52020480. Its totient is φ = 7879680.

The previous prime is 21013021. The next prime is 21013043. The reversal of 21013040 is 4031012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (21013043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91646 + ... + 91874.

It is an arithmetic number, because the mean of its divisors is an integer number (650256).

Almost surely, 2^21013040 is an apocalyptic number.

21013040 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 21013040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26010240).

21013040 is an abundant number, since it is smaller than the sum of its proper divisors (31007440).

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

21013040 is a wasteful number, since it uses less digits than its factorization.

21013040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310 (or 304 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21013040 is about 4583.9982547990. The cubic root of 21013040 is about 275.9495111735.

Adding to 21013040 its reverse (4031012), we get a palindrome (25044052).

The spelling of 21013040 in words is "twenty-one million, thirteen thousand, forty".