21891416064 has 256 divisors, whose sum is σ = 69079132800. Its totient is φ = 6033506304.

The previous prime is 21891416059. The next prime is 21891416089. The reversal of 21891416064 is 46061419812.

It is a tau number, because it is divible by the number of its divisors (256).

It is a super-3 number, since 3×21891416064³ (a number of 32 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19955164 + ... + 19956260.

Almost surely, 2^21891416064 is an apocalyptic number.

21891416064 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21891416064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34539566400).

21891416064 is an abundant number, since it is smaller than the sum of its proper divisors (47187716736).

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

21891416064 is an equidigital number, since it uses as much as digits as its factorization.

21891416064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1166 (or 1138 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 42.

The spelling of 21891416064 in words is "twenty-one billion, eight hundred ninety-one million, four hundred sixteen thousand, sixty-four".