661644287 has 2 divisors, whose sum is σ = 661644288. Its totient is φ = 661644286.

The previous prime is 661644259. The next prime is 661644299. The reversal of 661644287 is 782446166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661644287 - 2¹⁴ = 661627903 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661604287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330822143 + 330822144.

It is an arithmetic number, because the mean of its divisors is an integer number (330822144).

Almost surely, 2^661644287 is an apocalyptic number.

661644287 is a deficient number, since it is larger than the sum of its proper divisors (1).

661644287 is an equidigital number, since it uses as much as digits as its factorization.

661644287 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 387072, while the sum is 44.

The square root of 661644287 is about 25722.4471425251. The cubic root of 661644287 is about 871.3812063185.

The spelling of 661644287 in words is "six hundred sixty-one million, six hundred forty-four thousand, two hundred eighty-seven".