21783440 has 60 divisors (see below), whose sum is σ = 58925916. Its totient is φ = 7467264.

The previous prime is 21783431. The next prime is 21783451. The reversal of 21783440 is 4438712.

It can be written as a sum of positive squares in 2 ways, for example, as 15147664 + 6635776 = 3892^2 + 2576^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1142 + ... + 6698.

Almost surely, 2^21783440 is an apocalyptic number.

21783440 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 21783440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29462958).

21783440 is an abundant number, since it is smaller than the sum of its proper divisors (37142476).

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

21783440 is a wasteful number, since it uses less digits than its factorization.

21783440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5584 (or 5571 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 21783440 is about 4667.2732939051. The cubic root of 21783440 is about 279.2814911427.

The spelling of 21783440 in words is "twenty-one million, seven hundred eighty-three thousand, four hundred forty".