21161923820 has 12 divisors (see below), whose sum is σ = 44440040064. Its totient is φ = 8464769520.

The previous prime is 21161923753. The next prime is 21161923829. The reversal of 21161923820 is 2832916112.

It is not an unprimeable number, because it can be changed into a prime (21161923829) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 529048076 + ... + 529048115.

It is an arithmetic number, because the mean of its divisors is an integer number (3703336672).

Almost surely, 2^21161923820 is an apocalyptic number.

21161923820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21161923820 is an abundant number, since it is smaller than the sum of its proper divisors (23278116244).

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

21161923820 is a wasteful number, since it uses less digits than its factorization.

21161923820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1058096200 (or 1058096198 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 35.

The spelling of 21161923820 in words is "twenty-one billion, one hundred sixty-one million, nine hundred twenty-three thousand, eight hundred twenty".