21321040 has 120 divisors (see below), whose sum is σ = 57183840. Its totient is φ = 7368192.

The previous prime is 21321031. The next prime is 21321067. The reversal of 21321040 is 4012312.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a self number, because there is not a number n which added to its sum of digits gives 21321040.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 256839 + ... + 256921.

It is an arithmetic number, because the mean of its divisors is an integer number (476532).

Almost surely, 2^21321040 is an apocalyptic number.

21321040 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 21321040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28591920).

21321040 is an abundant number, since it is smaller than the sum of its proper divisors (35862800).

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

21321040 is a wasteful number, since it uses less digits than its factorization.

21321040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141 (or 122 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21321040 is about 4617.4711693740. The cubic root of 21321040 is about 277.2912262462.

Adding to 21321040 its reverse (4012312), we get a palindrome (25333352).

The spelling of 21321040 in words is "twenty-one million, three hundred twenty-one thousand, forty".