21711820 has 48 divisors (see below), whose sum is σ = 49603680. Its totient is φ = 7934976.

The previous prime is 21711803. The next prime is 21711827. The reversal of 21711820 is 2811712.

It is a junction number, because it is equal to n+sod(n) for n = 21711791 and 21711800.

It is not an unprimeable number, because it can be changed into a prime (21711827) by changing a digit.

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, 29011 + ... + 29749.

It is an arithmetic number, because the mean of its divisors is an integer number (1033410).

Almost surely, 2^21711820 is an apocalyptic number.

21711820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21711820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24801840).

21711820 is an abundant number, since it is smaller than the sum of its proper divisors (27891860).

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

21711820 is a wasteful number, since it uses less digits than its factorization.

21711820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 874 (or 872 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21711820 is about 4659.5944029497. The cubic root of 21711820 is about 278.9750794577.

The spelling of 21711820 in words is "twenty-one million, seven hundred eleven thousand, eight hundred twenty".