21320424 has 24 divisors (see below), whose sum is σ = 57743010. Its totient is φ = 7106784.

The previous prime is 21320407. The next prime is 21320447. The reversal of 21320424 is 42402312.

It can be written as a sum of positive squares in only one way, i.e., 20088324 + 1232100 = 4482^2 + 1110^2 .

It is a tau number, because it is divible by the number of its divisors (24).

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

It is a junction number, because it is equal to n+sod(n) for n = 21320397 and 21320406.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 147987 + ... + 148130.

Almost surely, 2^21320424 is an apocalyptic number.

21320424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21320424 is an abundant number, since it is smaller than the sum of its proper divisors (36422586).

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

21320424 is a wasteful number, since it uses less digits than its factorization.

21320424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296129 (or 296122 counting only the distinct ones).

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

The square root of 21320424 is about 4617.4044657145. The cubic root of 21320424 is about 277.2885557535.

Adding to 21320424 its reverse (42402312), we get a palindrome (63722736).

The spelling of 21320424 in words is "twenty-one million, three hundred twenty thousand, four hundred twenty-four".