21218620 has 24 divisors (see below), whose sum is σ = 45509184. Its totient is φ = 8306496.

The previous prime is 21218599. The next prime is 21218629. The reversal of 21218620 is 2681212.

It is a junction number, because it is equal to n+sod(n) for n = 21218591 and 21218600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21218629) 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, 10347 + ... + 12226.

It is an arithmetic number, because the mean of its divisors is an integer number (1896216).

Almost surely, 2^21218620 is an apocalyptic number.

21218620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21218620 is an abundant number, since it is smaller than the sum of its proper divisors (24290564).

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

21218620 is a wasteful number, since it uses less digits than its factorization.

21218620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22629 (or 22627 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 21218620 is about 4606.3673322912. The cubic root of 21218620 is about 276.8465049053.

Adding to 21218620 its reverse (2681212), we get a palindrome (23899832).

The spelling of 21218620 in words is "twenty-one million, two hundred eighteen thousand, six hundred twenty".