661805759 has 4 divisors (see below), whose sum is σ = 662807640. Its totient is φ = 660803880.

The previous prime is 661805747. The next prime is 661805761. The reversal of 661805759 is 957508166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 957508166 = 2 ⋅478754083.

It is a cyclic number.

It is not a de Polignac number, because 661805759 - 2⁸ = 661805503 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661805719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 499949 + ... + 501270.

It is an arithmetic number, because the mean of its divisors is an integer number (165701910).

Almost surely, 2^661805759 is an apocalyptic number.

661805759 is a deficient number, since it is larger than the sum of its proper divisors (1001881).

661805759 is a wasteful number, since it uses less digits than its factorization.

661805759 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1001880.

The product of its (nonzero) digits is 453600, while the sum is 47.

The square root of 661805759 is about 25725.5856881821. The cubic root of 661805759 is about 871.4520864094.

The spelling of 661805759 in words is "six hundred sixty-one million, eight hundred five thousand, seven hundred fifty-nine".