21001768256 has 112 divisors (see below), whose sum is σ = 50606553600. Its totient is φ = 8446975488.

The previous prime is 21001768253. The next prime is 21001768301. The reversal of 21001768256 is 65286710012.

It is a tau number, because it is divible by the number of its divisors (112).

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001768253) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 899255 + ... + 922313.

Almost surely, 2^21001768256 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21001768256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25303276800).

21001768256 is an abundant number, since it is smaller than the sum of its proper divisors (29604785344).

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

21001768256 is a wasteful number, since it uses less digits than its factorization.

21001768256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23204 (or 23194 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 38.

The spelling of 21001768256 in words is "twenty-one billion, one million, seven hundred sixty-eight thousand, two hundred fifty-six".