645064611661 has 2 divisors, whose sum is σ = 645064611662. Its totient is φ = 645064611660.

The previous prime is 645064611619. The next prime is 645064611673. The reversal of 645064611661 is 166116460546.

645064611661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 512361050436 + 132703561225 = 715794^2 + 364285^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645064611661 is a prime.

It is a super-2 number, since 2×645064611661² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645064615661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322532305830 + 322532305831.

It is an arithmetic number, because the mean of its divisors is an integer number (322532305831).

Almost surely, 2^645064611661 is an apocalyptic number.

It is an amenable number.

645064611661 is a deficient number, since it is larger than the sum of its proper divisors (1).

645064611661 is an equidigital number, since it uses as much as digits as its factorization.

645064611661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 622080, while the sum is 46.

The spelling of 645064611661 in words is "six hundred forty-five billion, sixty-four million, six hundred eleven thousand, six hundred sixty-one".