21809899020 has 288 divisors, whose sum is σ = 77560314048. Its totient is φ = 4538032128.

The previous prime is 21809899003. The next prime is 21809899039. The reversal of 21809899020 is 2099890812.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2786152 + ... + 2793968.

It is an arithmetic number, because the mean of its divisors is an integer number (269306646).

Almost surely, 2^21809899020 is an apocalyptic number.

21809899020 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 21809899020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38780157024).

21809899020 is an abundant number, since it is smaller than the sum of its proper divisors (55750415028).

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

21809899020 is a wasteful number, since it uses less digits than its factorization.

21809899020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7929 (or 7920 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 48.

The spelling of 21809899020 in words is "twenty-one billion, eight hundred nine million, eight hundred ninety-nine thousand, twenty".