66561022072656 has 640 divisors, whose sum is σ = 206086809600000. Its totient is φ = 20495160483840.

The previous prime is 66561022072607. The next prime is 66561022072681. The reversal of 66561022072656 is 65627022016566.

66561022072656 is a `hidden beast` number, since 6 + 6 + 561 + 0 + 2 + 2 + 0 + 7 + 26 + 56 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 36352277661 + ... + 36352279491.

It is an arithmetic number, because the mean of its divisors is an integer number (322010640000).

Almost surely, 2^{66561022072656} 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 66561022072656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103043404800000).

66561022072656 is an abundant number, since it is smaller than the sum of its proper divisors (139525787527344).

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

66561022072656 is a wasteful number, since it uses less digits than its factorization.

66561022072656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2392 (or 2380 counting only the distinct ones).

The product of its (nonzero) digits is 10886400, while the sum is 54.

The spelling of 66561022072656 in words is "sixty-six trillion, five hundred sixty-one billion, twenty-two million, seventy-two thousand, six hundred fifty-six".