645160021 has 24 divisors (see below), whose sum is σ = 723945600. Its totient is φ = 574411200.

The previous prime is 645160007. The next prime is 645160037. The reversal of 645160021 is 120061546.

645160021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a de Polignac number, because none of the positive numbers 2^k-645160021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645160121) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1496676 + ... + 1497106.

It is an arithmetic number, because the mean of its divisors is an integer number (30164400).

Almost surely, 2^645160021 is an apocalyptic number.

It is an amenable number.

645160021 is a deficient number, since it is larger than the sum of its proper divisors (78785579).

645160021 is a wasteful number, since it uses less digits than its factorization.

645160021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 681 (or 670 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 645160021 is about 25400.0004133858. Note that the first 3 decimals coincide. The cubic root of 645160021 is about 864.0837061141.

The spelling of 645160021 in words is "six hundred forty-five million, one hundred sixty thousand, twenty-one".