645407221 has 2 divisors, whose sum is σ = 645407222. Its totient is φ = 645407220.

The previous prime is 645407183. The next prime is 645407237. The reversal of 645407221 is 122704546.

645407221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 621504900 + 23902321 = 24930^2 + 4889^2 .

It is a cyclic number.

It is not a de Polignac number, because 645407221 - 2²⁷ = 511189493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645407291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322703610 + 322703611.

It is an arithmetic number, because the mean of its divisors is an integer number (322703611).

Almost surely, 2^645407221 is an apocalyptic number.

It is an amenable number.

645407221 is a deficient number, since it is larger than the sum of its proper divisors (1).

645407221 is an equidigital number, since it uses as much as digits as its factorization.

645407221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13440, while the sum is 31.

The square root of 645407221 is about 25404.8660889996. The cubic root of 645407221 is about 864.1940530098.

The spelling of 645407221 in words is "six hundred forty-five million, four hundred seven thousand, two hundred twenty-one".