645399647 has 2 divisors, whose sum is σ = 645399648. Its totient is φ = 645399646.

The previous prime is 645399607. The next prime is 645399661. The reversal of 645399647 is 746993546.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645399647 - 2⁶ = 645399583 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645399607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322699823 + 322699824.

It is an arithmetic number, because the mean of its divisors is an integer number (322699824).

Almost surely, 2^645399647 is an apocalyptic number.

645399647 is a deficient number, since it is larger than the sum of its proper divisors (1).

645399647 is an equidigital number, since it uses as much as digits as its factorization.

645399647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4898880, while the sum is 53.

The square root of 645399647 is about 25404.7170226318. The cubic root of 645399647 is about 864.1906724922.

The spelling of 645399647 in words is "six hundred forty-five million, three hundred ninety-nine thousand, six hundred forty-seven".