21293440 has 128 divisors (see below), whose sum is σ = 59976000. Its totient is φ = 7225344.

The previous prime is 21293431. The next prime is 21293483. The reversal of 21293440 is 4439212.

It is a tau number, because it is divible by the number of its divisors (128).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 219472 + ... + 219568.

Almost surely, 2^21293440 is an apocalyptic number.

21293440 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 21293440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29988000).

21293440 is an abundant number, since it is smaller than the sum of its proper divisors (38682560).

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

21293440 is an frugal number, since it uses more digits than its factorization.

21293440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137 (or 111 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 21293440 is about 4614.4815526774. The cubic root of 21293440 is about 277.1715237898.

The spelling of 21293440 in words is "twenty-one million, two hundred ninety-three thousand, four hundred forty".