21285854820 has 36 divisors (see below), whose sum is σ = 64567093500. Its totient is φ = 5676227904.

The previous prime is 21285854791. The next prime is 21285854857. The reversal of 21285854820 is 2845858212.

21285854820 is a `hidden beast` number, since 2 + 1 + 2 + 8 + 585 + 48 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 12950895204 + 8334959616 = 113802^2 + 91296^2 .

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

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59127195 + ... + 59127554.

It is an arithmetic number, because the mean of its divisors is an integer number (1793530375).

Almost surely, 2^21285854820 is an apocalyptic number.

21285854820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21285854820 is an abundant number, since it is smaller than the sum of its proper divisors (43281238680).

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

21285854820 is a wasteful number, since it uses less digits than its factorization.

21285854820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118254764 (or 118254759 counting only the distinct ones).

The product of its (nonzero) digits is 409600, while the sum is 45.

The spelling of 21285854820 in words is "twenty-one billion, two hundred eighty-five million, eight hundred fifty-four thousand, eight hundred twenty".