21406993408 has 88 divisors (see below), whose sum is σ = 44619326928. Its totient is φ = 10256203776.

The previous prime is 21406993373. The next prime is 21406993409. The reversal of 21406993408 is 80439960412.

It is not an unprimeable number, because it can be changed into a prime (21406993409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2329110 + ... + 2338282.

It is an arithmetic number, because the mean of its divisors is an integer number (507037806).

Almost surely, 2^21406993408 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 21406993408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22309663464).

21406993408 is an abundant number, since it is smaller than the sum of its proper divisors (23212333520).

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

21406993408 is an equidigital number, since it uses as much as digits as its factorization.

21406993408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9289 (or 9271 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 46.

The spelling of 21406993408 in words is "twenty-one billion, four hundred six million, nine hundred ninety-three thousand, four hundred eight".