661816512000 has 1920 divisors, whose sum is σ = 2939687562240. Its totient is φ = 139744051200.

The previous prime is 661816511903. The next prime is 661816512043. The reversal of 661816512000 is 215618166.

661816512000 is a `hidden beast` number, since 6 + 61 + 81 + 6 + 512 + 0 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1920).

It is a super-2 number, since 2×661816512000² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

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, 4060223919 + ... + 4060224081.

It is an arithmetic number, because the mean of its divisors is an integer number (1531087272).

Almost surely, 2^661816512000 is an apocalyptic number.

661816512000 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 661816512000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1469843781120).

661816512000 is an abundant number, since it is smaller than the sum of its proper divisors (2277871050240).

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

661816512000 is a wasteful number, since it uses less digits than its factorization.

661816512000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281 (or 252 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The spelling of 661816512000 in words is "six hundred sixty-one billion, eight hundred sixteen million, five hundred twelve thousand".