645377221 has 2 divisors, whose sum is σ = 645377222. Its totient is φ = 645377220.

The previous prime is 645377219. The next prime is 645377233. The reversal of 645377221 is 122773546.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 488852100 + 156525121 = 22110^2 + 12511^2 .

It is a cyclic number.

It is not a de Polignac number, because 645377221 - 2¹ = 645377219 is a prime.

Together with 645377219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645377321) 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 as a sum of consecutive naturals, namely, 322688610 + 322688611.

It is an arithmetic number, because the mean of its divisors is an integer number (322688611).

Almost surely, 2^645377221 is an apocalyptic number.

It is an amenable number.

645377221 is a deficient number, since it is larger than the sum of its proper divisors (1).

645377221 is an equidigital number, since it uses as much as digits as its factorization.

645377221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 70560, while the sum is 37.

The square root of 645377221 is about 25404.2756440722. The cubic root of 645377221 is about 864.1806628987.

The spelling of 645377221 in words is "six hundred forty-five million, three hundred seventy-seven thousand, two hundred twenty-one".