661663513340640 has 72 divisors (see below), whose sum is σ = 2257926739279848. Its totient is φ = 176443603557120.

The previous prime is 661663513340581. The next prime is 661663513340651. The reversal of 661663513340640 is 46043315366166.

661663513340640 is a `hidden beast` number, since 6 + 6 + 1 + 6 + 63 + 5 + 133 + 406 + 40 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a super-3 number, since 3×661663513340640³ (a number of 45 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 229744274026 + ... + 229744276905.

It is an arithmetic number, because the mean of its divisors is an integer number (31360093601109).

Almost surely, 2^{661663513340640} is an apocalyptic number.

661663513340640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661663513340640 is an abundant number, since it is smaller than the sum of its proper divisors (1596263225939208).

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

661663513340640 is a wasteful number, since it uses less digits than its factorization.

661663513340640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 459488550952 (or 459488550941 counting only the distinct ones).

The product of its (nonzero) digits is 16796160, while the sum is 54.

The spelling of 661663513340640 in words is "six hundred sixty-one trillion, six hundred sixty-three billion, five hundred thirteen million, three hundred forty thousand, six hundred forty".