645388531 has 2 divisors, whose sum is σ = 645388532. Its totient is φ = 645388530.

The previous prime is 645388529. The next prime is 645388577. The reversal of 645388531 is 135883546.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645388531 - 2¹ = 645388529 is a prime.

It is a super-2 number, since 2×645388531² = 833052711892675922, which contains 22 as substring.

Together with 645388529, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (645388511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322694265 + 322694266.

It is an arithmetic number, because the mean of its divisors is an integer number (322694266).

Almost surely, 2^645388531 is an apocalyptic number.

645388531 is a deficient number, since it is larger than the sum of its proper divisors (1).

645388531 is an equidigital number, since it uses as much as digits as its factorization.

645388531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 345600, while the sum is 43.

The square root of 645388531 is about 25404.4982434214. The cubic root of 645388531 is about 864.1857110193.

The spelling of 645388531 in words is "six hundred forty-five million, three hundred eighty-eight thousand, five hundred thirty-one".