21323220 has 48 divisors (see below), whose sum is σ = 59911488. Its totient is φ = 5666560.

The previous prime is 21323209. The next prime is 21323261. The reversal of 21323220 is 2232312.

It is a super-2 number, since 2×21323220² = 909359422336800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21323220.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 27640 + ... + 28400.

It is an arithmetic number, because the mean of its divisors is an integer number (1248156).

Almost surely, 2^21323220 is an apocalyptic number.

21323220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21323220 is an abundant number, since it is smaller than the sum of its proper divisors (38588268).

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

21323220 is a wasteful number, since it uses less digits than its factorization.

21323220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1240 (or 1238 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 15.

The square root of 21323220 is about 4617.7072232873. The cubic root of 21323220 is about 277.3006766024.

Adding to 21323220 its reverse (2232312), we get a palindrome (23555532).

The spelling of 21323220 in words is "twenty-one million, three hundred twenty-three thousand, two hundred twenty".