21017696028 has 72 divisors (see below), whose sum is σ = 57297517200. Its totient is φ = 5978794752.

The previous prime is 21017696027. The next prime is 21017696039. The reversal of 21017696028 is 82069671012.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21017696027) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 56608 + ... + 212696.

It is an arithmetic number, because the mean of its divisors is an integer number (795798850).

Almost surely, 2^21017696028 is an apocalyptic number.

21017696028 is a gapful number since it is divisible by the number (28) 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 21017696028, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28648758600).

21017696028 is an abundant number, since it is smaller than the sum of its proper divisors (36279821172).

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

21017696028 is a wasteful number, since it uses less digits than its factorization.

21017696028 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156339 (or 156330 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 42.

The spelling of 21017696028 in words is "twenty-one billion, seventeen million, six hundred ninety-six thousand, twenty-eight".