645607121 has 4 divisors (see below), whose sum is σ = 645708132. Its totient is φ = 645506112.

The previous prime is 645607069. The next prime is 645607129. The reversal of 645607121 is 121706546.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 90345025 + 555262096 = 9505^2 + 23564^2 .

It is a cyclic number.

It is not a de Polignac number, because 645607121 - 2⁶ = 645607057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645607129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40220 + ... + 53933.

It is an arithmetic number, because the mean of its divisors is an integer number (161427033).

Almost surely, 2^645607121 is an apocalyptic number.

It is an amenable number.

645607121 is a deficient number, since it is larger than the sum of its proper divisors (101011).

645607121 is an equidigital number, since it uses as much as digits as its factorization.

645607121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101010.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 645607121 is about 25408.8000700545. The cubic root of 645607121 is about 864.2832651916.

The spelling of 645607121 in words is "six hundred forty-five million, six hundred seven thousand, one hundred twenty-one".