645540481 has 2 divisors, whose sum is σ = 645540482. Its totient is φ = 645540480.

The previous prime is 645540479. The next prime is 645540587. The reversal of 645540481 is 184045546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 575232256 + 70308225 = 23984^2 + 8385^2 .

It is a cyclic number.

It is not a de Polignac number, because 645540481 - 2¹ = 645540479 is a prime.

It is a super-2 number, since 2×645540481² = 833445025219422722, which contains 22 as substring.

Together with 645540479, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 645540481.

It is not a weakly prime, because it can be changed into another prime (645540451) 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 as a sum of consecutive naturals, namely, 322770240 + 322770241.

It is an arithmetic number, because the mean of its divisors is an integer number (322770241).

Almost surely, 2^645540481 is an apocalyptic number.

It is an amenable number.

645540481 is a deficient number, since it is larger than the sum of its proper divisors (1).

645540481 is an equidigital number, since it uses as much as digits as its factorization.

645540481 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 76800, while the sum is 37.

The square root of 645540481 is about 25407.4886795212. The cubic root of 645540481 is about 864.2535268689.

Adding to 645540481 its product of nonzero digits (76800), we get a square (645617281 = 25409²).

The spelling of 645540481 in words is "six hundred forty-five million, five hundred forty thousand, four hundred eighty-one".