66211557191640 has 768 divisors, whose sum is σ = 265962536985600. Its totient is φ = 13945121574912.

The previous prime is 66211557191609. The next prime is 66211557191651. The reversal of 66211557191640 is 4619175511266.

66211557191640 is a `hidden beast` number, since 6 + 6 + 2 + 1 + 1 + 5 + 571 + 9 + 1 + 64 + 0 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 7321852959 + ... + 7321862001.

It is an arithmetic number, because the mean of its divisors is an integer number (346305386700).

Almost surely, 2^{66211557191640} is an apocalyptic number.

66211557191640 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 66211557191640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132981268492800).

66211557191640 is an abundant number, since it is smaller than the sum of its proper divisors (199750979793960).

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

66211557191640 is a wasteful number, since it uses less digits than its factorization.

66211557191640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13256 (or 13249 counting only the distinct ones).

The product of its (nonzero) digits is 2721600, while the sum is 54.

The spelling of 66211557191640 in words is "sixty-six trillion, two hundred eleven billion, five hundred fifty-seven million, one hundred ninety-one thousand, six hundred forty".