1660643261 has 2 divisors, whose sum is σ = 1660643262. Its totient is φ = 1660643260.

The previous prime is 1660643239. The next prime is 1660643357. The reversal of 1660643261 is 1623460661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1584517636 + 76125625 = 39806^2 + 8725^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1660643261 is a prime.

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 (1660643221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830321630 + 830321631.

It is an arithmetic number, because the mean of its divisors is an integer number (830321631).

Almost surely, 2^1660643261 is an apocalyptic number.

It is an amenable number.

1660643261 is a deficient number, since it is larger than the sum of its proper divisors (1).

1660643261 is an equidigital number, since it uses as much as digits as its factorization.

1660643261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 35.

The square root of 1660643261 is about 40750.9909204672. The cubic root of 1660643261 is about 1184.2010699595.

The spelling of 1660643261 in words is "one billion, six hundred sixty million, six hundred forty-three thousand, two hundred sixty-one".