21678240 has 96 divisors (see below), whose sum is σ = 71910720. Its totient is φ = 5474304.

The previous prime is 21678211. The next prime is 21678253. The reversal of 21678240 is 4287612.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21678198 and 21678207.

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, 7932 + ... + 10308.

It is an arithmetic number, because the mean of its divisors is an integer number (749070).

Almost surely, 2^21678240 is an apocalyptic number.

21678240 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 21678240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35955360).

21678240 is an abundant number, since it is smaller than the sum of its proper divisors (50232480).

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

21678240 is a wasteful number, since it uses less digits than its factorization.

21678240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2414 (or 2406 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 21678240 is about 4655.9896907102. The cubic root of 21678240 is about 278.8311821566.

The spelling of 21678240 in words is "twenty-one million, six hundred seventy-eight thousand, two hundred forty".