21019017128 has 16 divisors (see below), whose sum is σ = 40475810580.
Its totient is φ = 10225467648.
The previous prime is 21019017127. The next prime is 21019017143. The reversal of 21019017128 is 82171091012.
It can be written as a sum of positive squares in 2 ways, for example, as 20833458244 + 185558884 = 144338^2 + 13622^2
It is a junction number, because it is equal to n+sod(n) for n = 21019017094 and 21019017103.
It is not an unprimeable number, because it can be changed into a prime (21019017127) 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, 35504801 + ... + 35505392.
Almost surely, 221019017128 is an apocalyptic number.
It is an amenable number.
21019017128 is a deficient number, since it is larger than the sum of its proper divisors (19456793452).
21019017128 is a wasteful number, since it uses less digits than its factorization.
21019017128 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 71010236 (or 71010232 counting only the distinct ones).
The product of its (nonzero) digits is 2016, while the sum is 32.
The spelling of 21019017128 in words is "twenty-one billion, nineteen million, seventeen thousand, one hundred twenty-eight".