661804416 has 384 divisors, whose sum is σ = 2405894400. Its totient is φ = 169979904.

The previous prime is 661804391. The next prime is 661804439. The reversal of 661804416 is 614408166.

661804416 is a `hidden beast` number, since 66 + 180 + 4 + 416 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

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

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 6185035 + ... + 6185141.

It is an arithmetic number, because the mean of its divisors is an integer number (6265350).

Almost surely, 2^661804416 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 661804416, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1202947200).

661804416 is an abundant number, since it is smaller than the sum of its proper divisors (1744089984).

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

661804416 is a wasteful number, since it uses less digits than its factorization.

661804416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206 (or 191 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 661804416 is about 25725.5595857505. The cubic root of 661804416 is about 871.4514969308.

The spelling of 661804416 in words is "six hundred sixty-one million, eight hundred four thousand, four hundred sixteen".