645868961537 has 2 divisors, whose sum is σ = 645868961538. Its totient is φ = 645868961536.

The previous prime is 645868961461. The next prime is 645868961567. The reversal of 645868961537 is 735169868546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 361653093376 + 284215868161 = 601376^2 + 533119^2 .

It is a cyclic number.

It is not a de Polignac number, because 645868961537 - 2¹⁸ = 645868699393 is a prime.

It is not a weakly prime, because it can be changed into another prime (645868961567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322934480768 + 322934480769.

It is an arithmetic number, because the mean of its divisors is an integer number (322934480769).

Almost surely, 2^645868961537 is an apocalyptic number.

It is an amenable number.

645868961537 is a deficient number, since it is larger than the sum of its proper divisors (1).

645868961537 is an equidigital number, since it uses as much as digits as its factorization.

645868961537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 261273600, while the sum is 68.

The spelling of 645868961537 in words is "six hundred forty-five billion, eight hundred sixty-eight million, nine hundred sixty-one thousand, five hundred thirty-seven".