21855280 has 40 divisors (see below), whose sum is σ = 51059232. Its totient is φ = 8699904.

The previous prime is 21855277. The next prime is 21855283. The reversal of 21855280 is 8255812.

It is an interprime number because it is at equal distance from previous prime (21855277) and next prime (21855283).

It is a tau number, because it is divible by the number of its divisors (40).

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21855283) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20029 + ... + 21091.

Almost surely, 2^21855280 is an apocalyptic number.

21855280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21855280 is an abundant number, since it is smaller than the sum of its proper divisors (29203952).

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

21855280 is a wasteful number, since it uses less digits than its factorization.

21855280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1333 (or 1327 counting only the distinct ones).

The product of its (nonzero) digits is 6400, while the sum is 31.

The square root of 21855280 is about 4674.9631014587. The cubic root of 21855280 is about 279.5881700790.

The spelling of 21855280 in words is "twenty-one million, eight hundred fifty-five thousand, two hundred eighty".