661005641 has 2 divisors, whose sum is σ = 661005642. Its totient is φ = 661005640.

The previous prime is 661005619. The next prime is 661005659. The reversal of 661005641 is 146500166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 391881616 + 269124025 = 19796^2 + 16405^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661005641 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (661005341) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330502820 + 330502821.

It is an arithmetic number, because the mean of its divisors is an integer number (330502821).

Almost surely, 2^661005641 is an apocalyptic number.

It is an amenable number.

661005641 is a deficient number, since it is larger than the sum of its proper divisors (1).

661005641 is an equidigital number, since it uses as much as digits as its factorization.

661005641 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 661005641 is about 25710.0299688662. The cubic root of 661005641 is about 871.1007518596.

The spelling of 661005641 in words is "six hundred sixty-one million, five thousand, six hundred forty-one".