21783040 has 80 divisors (see below), whose sum is σ = 53425152. Its totient is φ = 8515584.

The previous prime is 21783037. The next prime is 21783059. The reversal of 21783040 is 4038712.

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

It is a junction number, because it is equal to n+sod(n) for n = 21782996 and 21783014.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 171457 + ... + 171583.

Almost surely, 2^21783040 is an apocalyptic number.

21783040 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 21783040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26712576).

21783040 is an abundant number, since it is smaller than the sum of its proper divisors (31642112).

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

21783040 is an equidigital number, since it uses as much as digits as its factorization.

21783040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217 (or 201 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21783040 is about 4667.2304421359. The cubic root of 21783040 is about 279.2797816900.

The spelling of 21783040 in words is "twenty-one million, seven hundred eighty-three thousand, forty".