21433840 has 40 divisors (see below), whose sum is σ = 50295888. Its totient is φ = 8494080.

The previous prime is 21433831. The next prime is 21433859. The reversal of 21433840 is 4833412.

It is a tau number, because it is divible by the number of its divisors (40).

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7855 + ... + 10225.

Almost surely, 2^21433840 is an apocalyptic number.

21433840 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 21433840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25147944).

21433840 is an abundant number, since it is smaller than the sum of its proper divisors (28862048).

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

21433840 is a wasteful number, since it uses less digits than its factorization.

21433840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2497 (or 2491 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 25.

The square root of 21433840 is about 4629.6695346428. The cubic root of 21433840 is about 277.7793739760.

The spelling of 21433840 in words is "twenty-one million, four hundred thirty-three thousand, eight hundred forty".