21293840 has 40 divisors (see below), whose sum is σ = 49818240. Its totient is φ = 8464256.

The previous prime is 21293803. The next prime is 21293861. The reversal of 21293840 is 4839212.

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

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, 13577 + ... + 15063.

It is an arithmetic number, because the mean of its divisors is an integer number (1245456).

Almost surely, 2^21293840 is an apocalyptic number.

21293840 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 21293840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24909120).

21293840 is an abundant number, since it is smaller than the sum of its proper divisors (28524400).

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

21293840 is a wasteful number, since it uses less digits than its factorization.

21293840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1679 (or 1673 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21293840 is about 4614.5248942876. The cubic root of 21293840 is about 277.1732593464.

The spelling of 21293840 in words is "twenty-one million, two hundred ninety-three thousand, eight hundred forty".