21682440 has 192 divisors, whose sum is σ = 78427440. Its totient is φ = 5160960.

The previous prime is 21682433. The next prime is 21682487. The reversal of 21682440 is 4428612.

21682440 is a `hidden beast` number, since 216 + 8 + 2 + 440 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 171396 + 21511044 = 414^2 + 4638^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 191824 + ... + 191936.

Almost surely, 2^21682440 is an apocalyptic number.

21682440 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 21682440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39213720).

21682440 is an abundant number, since it is smaller than the sum of its proper divisors (56745000).

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

21682440 is a wasteful number, since it uses less digits than its factorization.

21682440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184 (or 177 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 21682440 is about 4656.4407007928. The cubic root of 21682440 is about 278.8491881593.

It can be divided in two parts, 21682 and 440, that added together give a palindrome (22122).

The spelling of 21682440 in words is "twenty-one million, six hundred eighty-two thousand, four hundred forty".