661606511 has 2 divisors, whose sum is σ = 661606512. Its totient is φ = 661606510.

The previous prime is 661606487. The next prime is 661606513. The reversal of 661606511 is 115606166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661606511 - 2¹⁸ = 661344367 is a prime.

Together with 661606513, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661606513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330803255 + 330803256.

It is an arithmetic number, because the mean of its divisors is an integer number (330803256).

Almost surely, 2^661606511 is an apocalyptic number.

661606511 is a deficient number, since it is larger than the sum of its proper divisors (1).

661606511 is an equidigital number, since it uses as much as digits as its factorization.

661606511 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 661606511 is about 25721.7128317692. The cubic root of 661606511 is about 871.3646224211.

The spelling of 661606511 in words is "six hundred sixty-one million, six hundred six thousand, five hundred eleven".