21520242 has 40 divisors (see below), whose sum is σ = 48926592. Its totient is φ = 7068600.

The previous prime is 21520241. The next prime is 21520243. The reversal of 21520242 is 24202512.

It is an interprime number because it is at equal distance from previous prime (21520241) and next prime (21520243).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21520241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 10567 + ... + 12437.

Almost surely, 2^21520242 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21520242, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24463296).

21520242 is an abundant number, since it is smaller than the sum of its proper divisors (27406350).

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

21520242 is a wasteful number, since it uses less digits than its factorization.

21520242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1956 (or 1947 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21520242 is about 4638.9914852261. The cubic root of 21520242 is about 278.1521259071.

Adding to 21520242 its reverse (24202512), we get a palindrome (45722754).

The spelling of 21520242 in words is "twenty-one million, five hundred twenty thousand, two hundred forty-two".