21333840 has 80 divisors (see below), whose sum is σ = 72156096. Its totient is φ = 5171200.

The previous prime is 21333839. The next prime is 21333847. The reversal of 21333840 is 4833312.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21333840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21333847) 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, 1401 + ... + 6680.

Almost surely, 2^21333840 is an apocalyptic number.

21333840 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 21333840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36078048).

21333840 is an abundant number, since it is smaller than the sum of its proper divisors (50822256).

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

21333840 is a wasteful number, since it uses less digits than its factorization.

21333840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8108 (or 8102 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 21333840 is about 4618.8570014669. The cubic root of 21333840 is about 277.3467053669.

It can be divided in two parts, 21 and 333840, that multiplied together give a triangular number (7010640 = T₃₇₄₄).

The spelling of 21333840 in words is "twenty-one million, three hundred thirty-three thousand, eight hundred forty".