645640591 has 2 divisors, whose sum is σ = 645640592. Its totient is φ = 645640590.

The previous prime is 645640553. The next prime is 645640607. The reversal of 645640591 is 195046546.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645640591 - 2¹³ = 645632399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645640091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322820295 + 322820296.

It is an arithmetic number, because the mean of its divisors is an integer number (322820296).

Almost surely, 2^645640591 is an apocalyptic number.

645640591 is a deficient number, since it is larger than the sum of its proper divisors (1).

645640591 is an equidigital number, since it uses as much as digits as its factorization.

645640591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 129600, while the sum is 40.

The square root of 645640591 is about 25409.4586915975. The cubic root of 645640591 is about 864.2982005189.

The spelling of 645640591 in words is "six hundred forty-five million, six hundred forty thousand, five hundred ninety-one".