21683520 has 84 divisors (see below), whose sum is σ = 74592180. Its totient is φ = 5781504.

The previous prime is 21683509. The next prime is 21683531. The reversal of 21683520 is 2538612.

It is an interprime number because it is at equal distance from previous prime (21683509) and next prime (21683531).

It can be written as a sum of positive squares in 2 ways, for example, as 7485696 + 14197824 = 2736^2 + 3768^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 885 + ... + 6644.

Almost surely, 2^21683520 is an apocalyptic number.

21683520 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 21683520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37296090).

21683520 is an abundant number, since it is smaller than the sum of its proper divisors (52908660).

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

21683520 is a wasteful number, since it uses less digits than its factorization.

21683520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7552 (or 7539 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21683520 is about 4656.5566677535. The cubic root of 21683520 is about 278.8538178984.

The spelling of 21683520 in words is "twenty-one million, six hundred eighty-three thousand, five hundred twenty".