66655721620 has 24 divisors (see below), whose sum is σ = 140904021888. Its totient is φ = 26485716000.

The previous prime is 66655721609. The next prime is 66655721633. The reversal of 66655721620 is 2612755666.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 11032696 + ... + 11038735.

It is an arithmetic number, because the mean of its divisors is an integer number (5871000912).

Almost surely, 2^66655721620 is an apocalyptic number.

It is an amenable number.

66655721620 is an abundant number, since it is smaller than the sum of its proper divisors (74248300268).

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

66655721620 is a wasteful number, since it uses less digits than its factorization.

66655721620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22071591 (or 22071589 counting only the distinct ones).

The product of its (nonzero) digits is 907200, while the sum is 46.

The spelling of 66655721620 in words is "sixty-six billion, six hundred fifty-five million, seven hundred twenty-one thousand, six hundred twenty".