21811571620 has 24 divisors (see below), whose sum is σ = 45824547384. Its totient is φ = 8720772096.

The previous prime is 21811571609. The next prime is 21811571627. The reversal of 21811571620 is 2617511812.

It can be written as a sum of positive squares in 4 ways, for example, as 5460323236 + 16351248384 = 73894^2 + 127872^2 .

It is not an unprimeable number, because it can be changed into a prime (21811571627) 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 7 ways as a sum of consecutive naturals, for example, 194439 + ... + 285358.

It is an arithmetic number, because the mean of its divisors is an integer number (1909356141).

Almost surely, 2^21811571620 is an apocalyptic number.

21811571620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21811571620 is an abundant number, since it is smaller than the sum of its proper divisors (24012975764).

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

21811571620 is a wasteful number, since it uses less digits than its factorization.

21811571620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 482079 (or 482077 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 34.

The spelling of 21811571620 in words is "twenty-one billion, eight hundred eleven million, five hundred seventy-one thousand, six hundred twenty".