661957717 has 2 divisors, whose sum is σ = 661957718. Its totient is φ = 661957716.

The previous prime is 661957697. The next prime is 661957721. The reversal of 661957717 is 717759166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 635342436 + 26615281 = 25206^2 + 5159^2 .

It is a cyclic number.

It is not a de Polignac number, because 661957717 - 2¹⁹ = 661433429 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661957217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330978858 + 330978859.

It is an arithmetic number, because the mean of its divisors is an integer number (330978859).

Almost surely, 2^661957717 is an apocalyptic number.

It is an amenable number.

661957717 is a deficient number, since it is larger than the sum of its proper divisors (1).

661957717 is an equidigital number, since it uses as much as digits as its factorization.

661957717 is an evil number, because the sum of its binary digits is even.

The product of its digits is 555660, while the sum is 49.

The square root of 661957717 is about 25728.5389596844. The cubic root of 661957717 is about 871.5187796852.

The spelling of 661957717 in words is "six hundred sixty-one million, nine hundred fifty-seven thousand, seven hundred seventeen".