21806280 has 128 divisors (see below), whose sum is σ = 74102400. Its totient is φ = 5702400.

The previous prime is 21806269. The next prime is 21806293. The reversal of 21806280 is 8260812.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 65715 + ... + 66045.

It is an arithmetic number, because the mean of its divisors is an integer number (578925).

Almost surely, 2^21806280 is an apocalyptic number.

21806280 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 21806280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37051200).

21806280 is an abundant number, since it is smaller than the sum of its proper divisors (52296120).

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

21806280 is a wasteful number, since it uses less digits than its factorization.

21806280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 412 (or 402 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 21806280 is about 4669.7194776560. The cubic root of 21806280 is about 279.3790661991.

The spelling of 21806280 in words is "twenty-one million, eight hundred six thousand, two hundred eighty".