21320442 has 96 divisors (see below), whose sum is σ = 56306880. Its totient is φ = 5940000.

The previous prime is 21320407. The next prime is 21320447. The reversal of 21320442 is 24402312.

It is a super-2 number, since 2×21320442² = 909122494150728, which contains 22 as substring.

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 (21320447) 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 47 ways as a sum of consecutive naturals, for example, 84817 + ... + 85067.

It is an arithmetic number, because the mean of its divisors is an integer number (586530).

Almost surely, 2^21320442 is an apocalyptic number.

21320442 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21320442, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28153440).

21320442 is an abundant number, since it is smaller than the sum of its proper divisors (34986438).

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

21320442 is a wasteful number, since it uses less digits than its factorization.

21320442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297 (or 280 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21320442 is about 4617.4064148611. The cubic root of 21320442 is about 277.2886337881.

Adding to 21320442 its reverse (24402312), we get a palindrome (45722754).

The spelling of 21320442 in words is "twenty-one million, three hundred twenty thousand, four hundred forty-two".