661565011 has 2 divisors, whose sum is σ = 661565012. Its totient is φ = 661565010.

The previous prime is 661564999. The next prime is 661565041. The reversal of 661565011 is 110565166.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661565011 is a prime.

It is not a weakly prime, because it can be changed into another prime (661565041) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330782505 + 330782506.

It is an arithmetic number, because the mean of its divisors is an integer number (330782506).

Almost surely, 2^661565011 is an apocalyptic number.

661565011 is a deficient number, since it is larger than the sum of its proper divisors (1).

661565011 is an equidigital number, since it uses as much as digits as its factorization.

661565011 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5400, while the sum is 31.

The square root of 661565011 is about 25720.9061076782. The cubic root of 661565011 is about 871.3464029370.

The spelling of 661565011 in words is "six hundred sixty-one million, five hundred sixty-five thousand, eleven".