645251121 has 12 divisors (see below), whose sum is σ = 933674820. Its totient is φ = 429408000.

The previous prime is 645251083. The next prime is 645251141. The reversal of 645251121 is 121152546.

645251121 is a `hidden beast` number, since 645 + 2 + 5 + 1 + 12 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 190026225 + 455224896 = 13785^2 + 21336^2 .

It is not a de Polignac number, because 645251121 - 2¹⁹ = 644726833 is a prime.

It is a super-3 number, since 3×645251121³ (a number of 27 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (645251141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 57880 + ... + 68121.

It is an arithmetic number, because the mean of its divisors is an integer number (77806235).

Almost surely, 2^645251121 is an apocalyptic number.

It is an amenable number.

645251121 is a deficient number, since it is larger than the sum of its proper divisors (288423699).

645251121 is a wasteful number, since it uses less digits than its factorization.

645251121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126576 (or 126573 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 645251121 is about 25401.7936571416. The cubic root of 645251121 is about 864.1243752598.

The spelling of 645251121 in words is "six hundred forty-five million, two hundred fifty-one thousand, one hundred twenty-one".