21391846824 has 16 divisors (see below), whose sum is σ = 53479617120. Its totient is φ = 7130615600.

The previous prime is 21391846823. The next prime is 21391846843. The reversal of 21391846824 is 42864819312.

It is a super-2 number, since 2×21391846824² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21391846823) 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, 445663452 + ... + 445663499.

It is an arithmetic number, because the mean of its divisors is an integer number (3342476070).

Almost surely, 2^21391846824 is an apocalyptic number.

21391846824 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21391846824 is an abundant number, since it is smaller than the sum of its proper divisors (32087770296).

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

21391846824 is a wasteful number, since it uses less digits than its factorization.

21391846824 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 891326960 (or 891326956 counting only the distinct ones).

The product of its digits is 663552, while the sum is 48.

The spelling of 21391846824 in words is "twenty-one billion, three hundred ninety-one million, eight hundred forty-six thousand, eight hundred twenty-four".