645909557 has 2 divisors, whose sum is σ = 645909558. Its totient is φ = 645909556.

The previous prime is 645909527. The next prime is 645909571. The reversal of 645909557 is 755909546.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 517744516 + 128165041 = 22754^2 + 11321^2 .

It is a cyclic number.

It is not a de Polignac number, because 645909557 - 2⁸ = 645909301 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645909527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322954778 + 322954779.

It is an arithmetic number, because the mean of its divisors is an integer number (322954779).

Almost surely, 2^645909557 is an apocalyptic number.

It is an amenable number.

645909557 is a deficient number, since it is larger than the sum of its proper divisors (1).

645909557 is an equidigital number, since it uses as much as digits as its factorization.

645909557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1701000, while the sum is 50.

The square root of 645909557 is about 25414.7507758782. The cubic root of 645909557 is about 864.4182025549.

It can be divided in two parts, 64590 and 9557, that added together give a palindrome (74147).

The spelling of 645909557 in words is "six hundred forty-five million, nine hundred nine thousand, five hundred fifty-seven".