665250661 has 2 divisors, whose sum is σ = 665250662. Its totient is φ = 665250660.

The previous prime is 665250659. The next prime is 665250683. The reversal of 665250661 is 166052566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 593848161 + 71402500 = 24369^2 + 8450^2 .

It is a cyclic number.

It is not a de Polignac number, because 665250661 - 2¹ = 665250659 is a prime.

Together with 665250659, it forms a pair of twin primes.

It is equal to p_34544791 and since 665250661 and 34544791 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 665250661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665250611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332625330 + 332625331.

It is an arithmetic number, because the mean of its divisors is an integer number (332625331).

Almost surely, 2^665250661 is an apocalyptic number.

It is an amenable number.

665250661 is a deficient number, since it is larger than the sum of its proper divisors (1).

665250661 is an equidigital number, since it uses as much as digits as its factorization.

665250661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64800, while the sum is 37.

The square root of 665250661 is about 25792.4535668866. The cubic root of 665250661 is about 872.9615288767.

The spelling of 665250661 in words is "six hundred sixty-five million, two hundred fifty thousand, six hundred sixty-one".