661895639936 has 256 divisors, whose sum is σ = 1450939392000. Its totient is φ = 299911987200.

The previous prime is 661895639929. The next prime is 661895639957. The reversal of 661895639936 is 639936598166.

It is a self number, because there is not a number n which added to its sum of digits gives 661895639936.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1127590235 + ... + 1127590821.

It is an arithmetic number, because the mean of its divisors is an integer number (5667732000).

Almost surely, 2^661895639936 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 661895639936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (725469696000).

661895639936 is an abundant number, since it is smaller than the sum of its proper divisors (789043752064).

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

661895639936 is a wasteful number, since it uses less digits than its factorization.

661895639936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 941 (or 929 counting only the distinct ones).

The product of its digits is 340122240, while the sum is 71.

The spelling of 661895639936 in words is "six hundred sixty-one billion, eight hundred ninety-five million, six hundred thirty-nine thousand, nine hundred thirty-six".