661885897 has 2 divisors, whose sum is σ = 661885898. Its totient is φ = 661885896.

The previous prime is 661885849. The next prime is 661885949. The reversal of 661885897 is 798588166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 660695616 + 1190281 = 25704^2 + 1091^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661885897 is a prime.

It is not a weakly prime, because it can be changed into another prime (661885297) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330942948 + 330942949.

It is an arithmetic number, because the mean of its divisors is an integer number (330942949).

Almost surely, 2^661885897 is an apocalyptic number.

It is an amenable number.

661885897 is a deficient number, since it is larger than the sum of its proper divisors (1).

661885897 is an equidigital number, since it uses as much as digits as its factorization.

661885897 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5806080, while the sum is 58.

The square root of 661885897 is about 25727.1431954658. The cubic root of 661885897 is about 871.4872596747.

The spelling of 661885897 in words is "six hundred sixty-one million, eight hundred eighty-five thousand, eight hundred ninety-seven".