64991221680 has 960 divisors, whose sum is σ = 274001891328. Its totient is φ = 12370821120.

The previous prime is 64991221657. The next prime is 64991221699. The reversal of 64991221680 is 8612219946.

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

It is an unprimeable number.

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 191 ways as a sum of consecutive naturals, for example, 229650819 + ... + 229651101.

Almost surely, 2^64991221680 is an apocalyptic number.

64991221680 is a gapful number since it is divisible by the number (60) 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 64991221680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (137000945664).

64991221680 is an abundant number, since it is smaller than the sum of its proper divisors (209010669648).

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

64991221680 is a wasteful number, since it uses less digits than its factorization.

64991221680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 394 (or 371 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 48.

The spelling of 64991221680 in words is "sixty-four billion, nine hundred ninety-one million, two hundred twenty-one thousand, six hundred eighty".