66621680640 has 528 divisors, whose sum is σ = 239000842080. Its totient is φ = 17148149760.

The previous prime is 66621680569. The next prime is 66621680651. The reversal of 66621680640 is 4608612666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 338181022 + ... + 338181218.

It is an arithmetic number, because the mean of its divisors is an integer number (452653110).

Almost surely, 2^66621680640 is an apocalyptic number.

66621680640 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 66621680640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119500421040).

66621680640 is an abundant number, since it is smaller than the sum of its proper divisors (172379161440).

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

66621680640 is a wasteful number, since it uses less digits than its factorization.

66621680640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 448 (or 427 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 45.

The spelling of 66621680640 in words is "sixty-six billion, six hundred twenty-one million, six hundred eighty thousand, six hundred forty".