645562121 has 4 divisors (see below), whose sum is σ = 648241044. Its totient is φ = 642883200.

The previous prime is 645562117. The next prime is 645562147. The reversal of 645562121 is 121265546.

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 194212096 + 451350025 = 13936^2 + 21245^2 .

It is a cyclic number.

It is not a de Polignac number, because 645562121 - 2² = 645562117 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645562171) 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, 1339100 + ... + 1339581.

It is an arithmetic number, because the mean of its divisors is an integer number (162060261).

Almost surely, 2^645562121 is an apocalyptic number.

It is an amenable number.

645562121 is a deficient number, since it is larger than the sum of its proper divisors (2678923).

645562121 is a wasteful number, since it uses less digits than its factorization.

645562121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2678922.

The product of its digits is 14400, while the sum is 32.

The square root of 645562121 is about 25407.9145346485. The cubic root of 645562121 is about 864.2631840156.

The spelling of 645562121 in words is "six hundred forty-five million, five hundred sixty-two thousand, one hundred twenty-one".