645278409 has 48 divisors (see below), whose sum is σ = 1006716672. Its totient is φ = 397229184.

The previous prime is 645278393. The next prime is 645278429. The reversal of 645278409 is 904872546.

It is a happy number.

645278409 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 645278409 - 2⁴ = 645278393 is a prime.

It is not an unprimeable number, because it can be changed into a prime (645278429) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1324764 + ... + 1325250.

It is an arithmetic number, because the mean of its divisors is an integer number (20973264).

Almost surely, 2^645278409 is an apocalyptic number.

645278409 is a gapful number since it is divisible by the number (69) formed by its first and last digit.

It is an amenable number.

645278409 is a deficient number, since it is larger than the sum of its proper divisors (361438263).

645278409 is a wasteful number, since it uses less digits than its factorization.

645278409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 726 (or 723 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The square root of 645278409 is about 25402.3307788872. The cubic root of 645278409 is about 864.1365565087.

The spelling of 645278409 in words is "six hundred forty-five million, two hundred seventy-eight thousand, four hundred nine".