661239869 has 2 divisors, whose sum is σ = 661239870. Its totient is φ = 661239868.

The previous prime is 661239847. The next prime is 661239893. The reversal of 661239869 is 968932166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 446265625 + 214974244 = 21125^2 + 14662^2 .

It is a cyclic number.

It is not a de Polignac number, because 661239869 - 2⁸ = 661239613 is a prime.

It is a super-2 number, since 2×661239869² = 874476328710274322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661229869) 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, 330619934 + 330619935.

It is an arithmetic number, because the mean of its divisors is an integer number (330619935).

Almost surely, 2^661239869 is an apocalyptic number.

It is an amenable number.

661239869 is a deficient number, since it is larger than the sum of its proper divisors (1).

661239869 is an equidigital number, since it uses as much as digits as its factorization.

661239869 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 839808, while the sum is 50.

The square root of 661239869 is about 25714.5847526263. The cubic root of 661239869 is about 871.2036315119.

The spelling of 661239869 in words is "six hundred sixty-one million, two hundred thirty-nine thousand, eight hundred sixty-nine".