645345681 has 4 divisors (see below), whose sum is σ = 860460912. Its totient is φ = 430230452.

The previous prime is 645345641. The next prime is 645345689. The reversal of 645345681 is 186543546.

645345681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 645345681 - 2⁷ = 645345553 is a prime.

It is a super-2 number, since 2×645345681² = 832942095970707522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (645345689) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107557611 + ... + 107557616.

It is an arithmetic number, because the mean of its divisors is an integer number (215115228).

Almost surely, 2^645345681 is an apocalyptic number.

It is an amenable number.

645345681 is a deficient number, since it is larger than the sum of its proper divisors (215115231).

645345681 is a wasteful number, since it uses less digits than its factorization.

645345681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215115230.

The product of its digits is 345600, while the sum is 42.

The square root of 645345681 is about 25403.6548748404. The cubic root of 645345681 is about 864.1665849810.

The spelling of 645345681 in words is "six hundred forty-five million, three hundred forty-five thousand, six hundred eighty-one".