21864180 has 48 divisors (see below), whose sum is σ = 65931264. Its totient is φ = 5381760.

The previous prime is 21864121. The next prime is 21864187. The reversal of 21864180 is 8146812.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21864187) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13236 + ... + 14795.

It is an arithmetic number, because the mean of its divisors is an integer number (1373568).

Almost surely, 2^21864180 is an apocalyptic number.

21864180 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21864180 is an abundant number, since it is smaller than the sum of its proper divisors (44067084).

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

21864180 is a wasteful number, since it uses less digits than its factorization.

21864180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28056 (or 28054 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 21864180 is about 4675.9148837420. The cubic root of 21864180 is about 279.6261166228.

The spelling of 21864180 in words is "twenty-one million, eight hundred sixty-four thousand, one hundred eighty".