21129285820 has 24 divisors (see below), whose sum is σ = 45403397424. Its totient is φ = 8255162496.

The previous prime is 21129285811. The next prime is 21129285829. The reversal of 21129285820 is 2858292112.

It is an interprime number because it is at equal distance from previous prime (21129285811) and next prime (21129285829).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21129285829) 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 7 ways as a sum of consecutive naturals, for example, 12283609 + ... + 12285328.

It is an arithmetic number, because the mean of its divisors is an integer number (1891808226).

Almost surely, 2^21129285820 is an apocalyptic number.

21129285820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21129285820 is an abundant number, since it is smaller than the sum of its proper divisors (24274111604).

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

21129285820 is a wasteful number, since it uses less digits than its factorization.

21129285820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24568989 (or 24568987 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 40.

The spelling of 21129285820 in words is "twenty-one billion, one hundred twenty-nine million, two hundred eighty-five thousand, eight hundred twenty".