21686280 has 128 divisors (see below), whose sum is σ = 81146880. Its totient is φ = 4504320.

The previous prime is 21686279. The next prime is 21686281. The reversal of 21686280 is 8268612.

It is an interprime number because it is at equal distance from previous prime (21686279) and next prime (21686281).

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21686281) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8067 + ... + 10413.

It is an arithmetic number, because the mean of its divisors is an integer number (633960).

Almost surely, 2^21686280 is an apocalyptic number.

21686280 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 21686280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40573440).

21686280 is an abundant number, since it is smaller than the sum of its proper divisors (59460600).

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

21686280 is a wasteful number, since it uses less digits than its factorization.

21686280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2379 (or 2375 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 33.

The square root of 21686280 is about 4656.8530146441. The cubic root of 21686280 is about 278.8656487556.

It can be divided in two parts, 2168 and 6280, that added together give a palindrome (8448).

The spelling of 21686280 in words is "twenty-one million, six hundred eighty-six thousand, two hundred eighty".