21306020 has 24 divisors (see below), whose sum is σ = 44919168. Its totient is φ = 8488800.

The previous prime is 21305989. The next prime is 21306023. The reversal of 21306020 is 2060312.

It is a junction number, because it is equal to n+sod(n) for n = 21305986 and 21306004.

It is not an unprimeable number, because it can be changed into a prime (21306023) 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, 3455 + ... + 7385.

It is an arithmetic number, because the mean of its divisors is an integer number (1871632).

Almost surely, 2^21306020 is an apocalyptic number.

21306020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21306020 is an abundant number, since it is smaller than the sum of its proper divisors (23613148).

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

21306020 is a wasteful number, since it uses less digits than its factorization.

21306020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4211 (or 4209 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 21306020 is about 4615.8444514520. The cubic root of 21306020 is about 277.2260966431.

Adding to 21306020 its reverse (2060312), we get a palindrome (23366332).

The spelling of 21306020 in words is "twenty-one million, three hundred six thousand, twenty".