661843757 has 4 divisors (see below), whose sum is σ = 661923900. Its totient is φ = 661763616.

The previous prime is 661843747. The next prime is 661843759. The reversal of 661843757 is 757348166.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 262083721 + 399760036 = 16189^2 + 19994^2 .

It is a cyclic number.

It is not a de Polignac number, because 661843757 - 2¹⁴ = 661827373 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 (661843759) 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, 26048 + ... + 44745.

It is an arithmetic number, because the mean of its divisors is an integer number (165480975).

Almost surely, 2^661843757 is an apocalyptic number.

It is an amenable number.

661843757 is a deficient number, since it is larger than the sum of its proper divisors (80143).

661843757 is an equidigital number, since it uses as much as digits as its factorization.

661843757 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80142.

The product of its digits is 846720, while the sum is 47.

The square root of 661843757 is about 25726.3242030415. The cubic root of 661843757 is about 871.4687644161.

The spelling of 661843757 in words is "six hundred sixty-one million, eight hundred forty-three thousand, seven hundred fifty-seven".