645409871 has 2 divisors, whose sum is σ = 645409872. Its totient is φ = 645409870.

The previous prime is 645409859. The next prime is 645409939. The reversal of 645409871 is 178904546.

645409871 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645409871 - 2¹⁴ = 645393487 is a prime.

It is a Sophie Germain 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 (645402871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322704935 + 322704936.

It is an arithmetic number, because the mean of its divisors is an integer number (322704936).

Almost surely, 2^645409871 is an apocalyptic number.

645409871 is the 13580-th centered heptagonal number.

645409871 is a deficient number, since it is larger than the sum of its proper divisors (1).

645409871 is an equidigital number, since it uses as much as digits as its factorization.

645409871 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 241920, while the sum is 44.

The square root of 645409871 is about 25404.9182443085. The cubic root of 645409871 is about 864.1952357830.

The spelling of 645409871 in words is "six hundred forty-five million, four hundred nine thousand, eight hundred seventy-one".