645107521 has 8 divisors (see below), whose sum is σ = 652708224. Its totient is φ = 637526400.

The previous prime is 645107509. The next prime is 645107527. The reversal of 645107521 is 125701546.

645107521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 645107521 - 2⁹ = 645107009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645107527) 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, 67596 + ... + 76546.

It is an arithmetic number, because the mean of its divisors is an integer number (81588528).

Almost surely, 2^645107521 is an apocalyptic number.

It is an amenable number.

645107521 is a deficient number, since it is larger than the sum of its proper divisors (7600703).

645107521 is an equidigital number, since it uses as much as digits as its factorization.

645107521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9791.

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 645107521 is about 25398.9669278103. The cubic root of 645107521 is about 864.0602671616.

The spelling of 645107521 in words is "six hundred forty-five million, one hundred seven thousand, five hundred twenty-one".