21381390828 has 60 divisors (see below), whose sum is σ = 63880211472. Its totient is φ = 6108968160.

The previous prime is 21381390787. The next prime is 21381390829. The reversal of 21381390828 is 82809318312.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21381390829) 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 19 ways as a sum of consecutive naturals, for example, 4711443 + ... + 4715978.

Almost surely, 2^21381390828 is an apocalyptic number.

21381390828 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21381390828 is an abundant number, since it is smaller than the sum of its proper divisors (42498820644).

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

21381390828 is a wasteful number, since it uses less digits than its factorization.

21381390828 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9427444 (or 9427433 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 45.

The spelling of 21381390828 in words is "twenty-one billion, three hundred eighty-one million, three hundred ninety thousand, eight hundred twenty-eight".