21842820 has 36 divisors (see below), whose sum is σ = 66257100. Its totient is φ = 5824704.

The previous prime is 21842813. The next prime is 21842851. The reversal of 21842820 is 2824812.

21842820 is a `hidden beast` number, since 218 + 428 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 5391684 + 16451136 = 2322^2 + 4056^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 60495 + ... + 60854.

It is an arithmetic number, because the mean of its divisors is an integer number (1840475).

Almost surely, 2^21842820 is an apocalyptic number.

21842820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21842820 is an abundant number, since it is smaller than the sum of its proper divisors (44414280).

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

21842820 is a wasteful number, since it uses less digits than its factorization.

21842820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121364 (or 121359 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

The square root of 21842820 is about 4673.6302806277. The cubic root of 21842820 is about 279.5350276067.

The spelling of 21842820 in words is "twenty-one million, eight hundred forty-two thousand, eight hundred twenty".