21685480 has 48 divisors (see below), whose sum is σ = 49987980. Its totient is φ = 8466432.

The previous prime is 21685457. The next prime is 21685483. The reversal of 21685480 is 8458612.

21685480 = 173² + 174² + ... + 412².

It can be written as a sum of positive squares in 6 ways, for example, as 11329956 + 10355524 = 3366^2 + 3218^2 .

It is not an unprimeable number, because it can be changed into a prime (21685483) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 112264 + ... + 112456.

Almost surely, 2^21685480 is an apocalyptic number.

21685480 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 21685480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24993990).

21685480 is an abundant number, since it is smaller than the sum of its proper divisors (28302500).

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

21685480 is a wasteful number, since it uses less digits than its factorization.

21685480 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310 (or 253 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 34.

The square root of 21685480 is about 4656.7671189356. The cubic root of 21685480 is about 278.8622196250.

The spelling of 21685480 in words is "twenty-one million, six hundred eighty-five thousand, four hundred eighty".