21321340 has 12 divisors (see below), whose sum is σ = 44774856. Its totient is φ = 8528528.

The previous prime is 21321337. The next prime is 21321341. The reversal of 21321340 is 4312312.

It is a happy number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321341) 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 3 ways as a sum of consecutive naturals, for example, 533014 + ... + 533053.

It is an arithmetic number, because the mean of its divisors is an integer number (3731238).

Almost surely, 2^21321340 is an apocalyptic number.

21321340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21321340 is an abundant number, since it is smaller than the sum of its proper divisors (23453516).

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

21321340 is a wasteful number, since it uses less digits than its factorization.

21321340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1066076 (or 1066074 counting only the distinct ones).

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

The square root of 21321340 is about 4617.5036545735. The cubic root of 21321340 is about 277.2925267921.

Adding to 21321340 its reverse (4312312), we get a palindrome (25633652).

Subtracting from 21321340 its reverse (4312312), we obtain a triangular number (17009028 = T₅₈₃₂).

The spelling of 21321340 in words is "twenty-one million, three hundred twenty-one thousand, three hundred forty".