21085191220 has 24 divisors (see below), whose sum is σ = 44462641608. Its totient is φ = 8399078400.

The previous prime is 21085191191. The next prime is 21085191247. The reversal of 21085191220 is 2219158012.

It can be written as a sum of positive squares in 4 ways, for example, as 402724624 + 20682466596 = 20068^2 + 143814^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2182441 + ... + 2192080.

It is an arithmetic number, because the mean of its divisors is an integer number (1852610067).

Almost surely, 2^21085191220 is an apocalyptic number.

21085191220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21085191220 is an abundant number, since it is smaller than the sum of its proper divisors (23377450388).

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

21085191220 is a wasteful number, since it uses less digits than its factorization.

21085191220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4374771 (or 4374769 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 31.

The spelling of 21085191220 in words is "twenty-one billion, eighty-five million, one hundred ninety-one thousand, two hundred twenty".