643825517 has 2 divisors, whose sum is σ = 643825518. Its totient is φ = 643825516.

The previous prime is 643825459. The next prime is 643825519. The reversal of 643825517 is 715528346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 505080676 + 138744841 = 22474^2 + 11779^2 .

It is a cyclic number.

It is not a de Polignac number, because 643825517 - 2⁸ = 643825261 is a prime.

It is a super-2 number, since 2×643825517² = 829022592680634578, which contains 22 as substring.

Together with 643825519, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643825519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321912758 + 321912759.

It is an arithmetic number, because the mean of its divisors is an integer number (321912759).

Almost surely, 2^643825517 is an apocalyptic number.

It is an amenable number.

643825517 is a deficient number, since it is larger than the sum of its proper divisors (1).

643825517 is an equidigital number, since it uses as much as digits as its factorization.

643825517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 201600, while the sum is 41.

The square root of 643825517 is about 25373.7170513112. The cubic root of 643825517 is about 863.4875133804.

The spelling of 643825517 in words is "six hundred forty-three million, eight hundred twenty-five thousand, five hundred seventeen".