21287232768 has 144 divisors (see below), whose sum is σ = 61562009600. Its totient is φ = 6505297920.

The previous prime is 21287232763. The next prime is 21287232779. The reversal of 21287232768 is 86723278212.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287232763) 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, 428823 + ... + 475881.

Almost surely, 2^21287232768 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 21287232768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30781004800).

21287232768 is an abundant number, since it is smaller than the sum of its proper divisors (40274776832).

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

21287232768 is a wasteful number, since it uses less digits than its factorization.

21287232768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47128 (or 47114 counting only the distinct ones).

The product of its digits is 903168, while the sum is 48.

The spelling of 21287232768 in words is "twenty-one billion, two hundred eighty-seven million, two hundred thirty-two thousand, seven hundred sixty-eight".