21816020 has 24 divisors (see below), whose sum is σ = 46061568. Its totient is φ = 8679200.

The previous prime is 21815999. The next prime is 21816031. The reversal of 21816020 is 2061812.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21815983 and 21816001.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 965 + ... + 6675.

It is an arithmetic number, because the mean of its divisors is an integer number (1919232).

Almost surely, 2^21816020 is an apocalyptic number.

21816020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21816020 is an abundant number, since it is smaller than the sum of its proper divisors (24245548).

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

21816020 is a wasteful number, since it uses less digits than its factorization.

21816020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5911 (or 5909 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21816020 is about 4670.7622504255. The cubic root of 21816020 is about 279.4206558553.

Adding to 21816020 its reverse (2061812), we get a palindrome (23877832).

The spelling of 21816020 in words is "twenty-one million, eight hundred sixteen thousand, twenty".