21818540 has 12 divisors (see below), whose sum is σ = 45818976. Its totient is φ = 8727408.

The previous prime is 21818539. The next prime is 21818557. The reversal of 21818540 is 4581812.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 545444 + ... + 545483.

It is an arithmetic number, because the mean of its divisors is an integer number (3818248).

Almost surely, 2^21818540 is an apocalyptic number.

21818540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21818540 is an abundant number, since it is smaller than the sum of its proper divisors (24000436).

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

21818540 is a wasteful number, since it uses less digits than its factorization.

21818540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1090936 (or 1090934 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 29.

The square root of 21818540 is about 4671.0320058848. The cubic root of 21818540 is about 279.4314142023.

The spelling of 21818540 in words is "twenty-one million, eight hundred eighteen thousand, five hundred forty".