645820895890 has 16 divisors (see below), whose sum is σ = 1162495091160. Its totient is φ = 258324474240.

The previous prime is 645820895857. The next prime is 645820895899. The reversal of 645820895890 is 98598028546.

It can be written as a sum of positive squares in 4 ways, for example, as 397955320569 + 247865575321 = 630837^2 + 497861^2 .

It is not an unprimeable number, because it can be changed into a prime (645820895899) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 268606 + ... + 1167814.

Almost surely, 2^645820895890 is an apocalyptic number.

645820895890 is a deficient number, since it is larger than the sum of its proper divisors (516674195270).

645820895890 is a wasteful number, since it uses less digits than its factorization.

645820895890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 971037.

The product of its (nonzero) digits is 49766400, while the sum is 64.

The spelling of 645820895890 in words is "six hundred forty-five billion, eight hundred twenty million, eight hundred ninety-five thousand, eight hundred ninety".