661866757 has 8 divisors (see below), whose sum is σ = 671673600. Its totient is φ = 652073520.

The previous prime is 661866743. The next prime is 661866781. The reversal of 661866757 is 757668166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661866757 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 (661866727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 135988 + ... + 140770.

It is an arithmetic number, because the mean of its divisors is an integer number (83959200).

Almost surely, 2^661866757 is an apocalyptic number.

It is an amenable number.

661866757 is a deficient number, since it is larger than the sum of its proper divisors (9806843).

661866757 is a wasteful number, since it uses less digits than its factorization.

661866757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6803.

The product of its digits is 2540160, while the sum is 52.

The square root of 661866757 is about 25726.7712121051. The cubic root of 661866757 is about 871.4788592203.

The spelling of 661866757 in words is "six hundred sixty-one million, eight hundred sixty-six thousand, seven hundred fifty-seven".