643618973 has 2 divisors, whose sum is σ = 643618974. Its totient is φ = 643618972.

The previous prime is 643618961. The next prime is 643618999. The reversal of 643618973 is 379816346.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 639179524 + 4439449 = 25282^2 + 2107^2 .

It is a cyclic number.

It is not a de Polignac number, because 643618973 - 2¹² = 643614877 is a prime.

It is equal to p_33478895 and since 643618973 and 33478895 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 (643617973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321809486 + 321809487.

It is an arithmetic number, because the mean of its divisors is an integer number (321809487).

Almost surely, 2^643618973 is an apocalyptic number.

It is an amenable number.

643618973 is a deficient number, since it is larger than the sum of its proper divisors (1).

643618973 is an equidigital number, since it uses as much as digits as its factorization.

643618973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 653184, while the sum is 47.

The square root of 643618973 is about 25369.6466865426. The cubic root of 643618973 is about 863.3951657720.

The spelling of 643618973 in words is "six hundred forty-three million, six hundred eighteen thousand, nine hundred seventy-three".