661684842 has 192 divisors, whose sum is σ = 1915119360. Its totient is φ = 164882304.

The previous prime is 661684819. The next prime is 661684843. The reversal of 661684842 is 248486166.

661684842 is a `hidden beast` number, since 6 + 6 + 168 + 484 + 2 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661684843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1773768 + ... + 1774140.

It is an arithmetic number, because the mean of its divisors is an integer number (9974580).

Almost surely, 2^661684842 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661684842, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (957559680).

661684842 is an abundant number, since it is smaller than the sum of its proper divisors (1253434518).

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

661684842 is a wasteful number, since it uses less digits than its factorization.

661684842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 442 (or 417 counting only the distinct ones).

The product of its digits is 442368, while the sum is 45.

The square root of 661684842 is about 25723.2354496863. The cubic root of 661684842 is about 871.3990095115.

The spelling of 661684842 in words is "six hundred sixty-one million, six hundred eighty-four thousand, eight hundred forty-two".