645643279 has 2 divisors, whose sum is σ = 645643280. Its totient is φ = 645643278.

The previous prime is 645643267. The next prime is 645643307. The reversal of 645643279 is 972346546.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645643279 - 2¹⁷ = 645512207 is a prime.

It is equal to p_33578587 and since 645643279 and 33578587 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645646279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322821639 + 322821640.

It is an arithmetic number, because the mean of its divisors is an integer number (322821640).

Almost surely, 2^645643279 is an apocalyptic number.

645643279 is a deficient number, since it is larger than the sum of its proper divisors (1).

645643279 is an equidigital number, since it uses as much as digits as its factorization.

645643279 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1088640, while the sum is 46.

The square root of 645643279 is about 25409.5115852312. The cubic root of 645643279 is about 864.2993999635.

The spelling of 645643279 in words is "six hundred forty-five million, six hundred forty-three thousand, two hundred seventy-nine".