21365340 has 48 divisors (see below), whose sum is σ = 60510240. Its totient is φ = 5632000.

The previous prime is 21365303. The next prime is 21365347. The reversal of 21365340 is 4356312.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21365340.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365347) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3340 + ... + 7340.

It is an arithmetic number, because the mean of its divisors is an integer number (1260630).

Almost surely, 2^21365340 is an apocalyptic number.

21365340 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 21365340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30255120).

21365340 is an abundant number, since it is smaller than the sum of its proper divisors (39144900).

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

21365340 is a wasteful number, since it uses less digits than its factorization.

21365340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4102 (or 4100 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 24.

The square root of 21365340 is about 4622.2656782145. The cubic root of 21365340 is about 277.4831415779.

Subtracting from 21365340 its reverse (4356312), we obtain a triangular number (17009028 = T₅₈₃₂).

The spelling of 21365340 in words is "twenty-one million, three hundred sixty-five thousand, three hundred forty".