643968877 has 2 divisors, whose sum is σ = 643968878. Its totient is φ = 643968876.

The previous prime is 643968833. The next prime is 643968889. The reversal of 643968877 is 778869346.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 360012676 + 283956201 = 18974^2 + 16851^2 .

It is a cyclic number.

It is not a de Polignac number, because 643968877 - 2¹⁹ = 643444589 is a prime.

It is a super-2 number, since 2×643968877² = 829391829089282258, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643968077) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321984438 + 321984439.

It is an arithmetic number, because the mean of its divisors is an integer number (321984439).

Almost surely, 2^643968877 is an apocalyptic number.

It is an amenable number.

643968877 is a deficient number, since it is larger than the sum of its proper divisors (1).

643968877 is an equidigital number, since it uses as much as digits as its factorization.

643968877 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12192768, while the sum is 58.

The square root of 643968877 is about 25376.5418644858. The cubic root of 643968877 is about 863.5515992648.

The spelling of 643968877 in words is "six hundred forty-three million, nine hundred sixty-eight thousand, eight hundred seventy-seven".