661908717 has 6 divisors (see below), whose sum is σ = 956090382. Its totient is φ = 441272472.

The previous prime is 661908691. The next prime is 661908721. The reversal of 661908717 is 717809166.

It can be written as a sum of positive squares in only one way, i.e., 649944036 + 11964681 = 25494^2 + 3459^2 .

It is not a de Polignac number, because 661908717 - 2²² = 657714413 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661908517) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36772698 + ... + 36772715.

It is an arithmetic number, because the mean of its divisors is an integer number (159348397).

Almost surely, 2^661908717 is an apocalyptic number.

It is an amenable number.

661908717 is a deficient number, since it is larger than the sum of its proper divisors (294181665).

661908717 is a wasteful number, since it uses less digits than its factorization.

661908717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73545419 (or 73545416 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 45.

The square root of 661908717 is about 25727.5866921093. The cubic root of 661908717 is about 871.4972750519.

The spelling of 661908717 in words is "six hundred sixty-one million, nine hundred eight thousand, seven hundred seventeen".