661311021236500 has 192 divisors, whose sum is σ = 1512923172284160. Its totient is φ = 252189726835200.

The previous prime is 661311021236491. The next prime is 661311021236549. The reversal of 661311021236500 is 5632120113166.

It is a self number, because there is not a number n which added to its sum of digits gives 661311021236500.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2246787342 + ... + 2247081658.

It is an arithmetic number, because the mean of its divisors is an integer number (7879808188980).

Almost surely, 2^{661311021236500} 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 661311021236500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (756461586142080).

661311021236500 is an abundant number, since it is smaller than the sum of its proper divisors (851612151047660).

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

661311021236500 is a wasteful number, since it uses less digits than its factorization.

661311021236500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296315 (or 296303 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 37.

Adding to 661311021236500 its reverse (5632120113166), we get a palindrome (666943141349666).

The spelling of 661311021236500 in words is "six hundred sixty-one trillion, three hundred eleven billion, twenty-one million, two hundred thirty-six thousand, five hundred".