661065861 has 16 divisors (see below), whose sum is σ = 892928000. Its totient is φ = 434993328.

The previous prime is 661065851. The next prime is 661065869. The reversal of 661065861 is 168560166.

It is not a de Polignac number, because 661065861 - 2⁷ = 661065733 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 (661065869) 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 15 ways as a sum of consecutive naturals, for example, 71460 + ... + 80178.

It is an arithmetic number, because the mean of its divisors is an integer number (55808000).

Almost surely, 2^661065861 is an apocalyptic number.

It is an amenable number.

661065861 is a deficient number, since it is larger than the sum of its proper divisors (231862139).

661065861 is a wasteful number, since it uses less digits than its factorization.

661065861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9048.

The product of its (nonzero) digits is 51840, while the sum is 39.

The square root of 661065861 is about 25711.2010804630. The cubic root of 661065861 is about 871.1272045306.

The spelling of 661065861 in words is "six hundred sixty-one million, sixty-five thousand, eight hundred sixty-one".