21213020 has 24 divisors (see below), whose sum is σ = 44638944. Its totient is φ = 8467776.

The previous prime is 21213013. The next prime is 21213029. The reversal of 21213020 is 2031212.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21212992 and 21213010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213029) 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, 13937 + ... + 15383.

It is an arithmetic number, because the mean of its divisors is an integer number (1859956).

Almost surely, 2^21213020 is an apocalyptic number.

21213020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21213020 is an abundant number, since it is smaller than the sum of its proper divisors (23425924).

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

21213020 is a wasteful number, since it uses less digits than its factorization.

21213020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2189 (or 2187 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21213020 is about 4605.7594379212. The cubic root of 21213020 is about 276.8221477317.

Adding to 21213020 its reverse (2031212), we get a palindrome (23244232).

The spelling of 21213020 in words is "twenty-one million, two hundred thirteen thousand, twenty".