661860869 has 2 divisors, whose sum is σ = 661860870. Its totient is φ = 661860868.

The previous prime is 661860853. The next prime is 661860889. The reversal of 661860869 is 968068166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 618168769 + 43692100 = 24863^2 + 6610^2 .

It is a cyclic number.

It is not a de Polignac number, because 661860869 - 2⁴ = 661860853 is a prime.

It is a super-2 number, since 2×661860869² = 876119619826870322, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661860889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330930434 + 330930435.

It is an arithmetic number, because the mean of its divisors is an integer number (330930435).

Almost surely, 2^661860869 is an apocalyptic number.

It is an amenable number.

661860869 is a deficient number, since it is larger than the sum of its proper divisors (1).

661860869 is an equidigital number, since it uses as much as digits as its factorization.

661860869 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 746496, while the sum is 50.

The square root of 661860869 is about 25726.6567785245. The cubic root of 661860869 is about 871.4762749727.

The spelling of 661860869 in words is "six hundred sixty-one million, eight hundred sixty thousand, eight hundred sixty-nine".