645871399 has 2 divisors, whose sum is σ = 645871400. Its totient is φ = 645871398.

The previous prime is 645871381. The next prime is 645871411. The reversal of 645871399 is 993178546.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645871399 - 2²¹ = 643774247 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645821399) 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, 322935699 + 322935700.

It is an arithmetic number, because the mean of its divisors is an integer number (322935700).

Almost surely, 2^645871399 is an apocalyptic number.

645871399 is a deficient number, since it is larger than the sum of its proper divisors (1).

645871399 is an equidigital number, since it uses as much as digits as its factorization.

645871399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1632960, while the sum is 52.

The square root of 645871399 is about 25414.0000590226. Note that the first 4 decimals coincide. The cubic root of 645871399 is about 864.4011799862.

The spelling of 645871399 in words is "six hundred forty-five million, eight hundred seventy-one thousand, three hundred ninety-nine".