643542637 has 2 divisors, whose sum is σ = 643542638. Its totient is φ = 643542636.

The previous prime is 643542629. The next prime is 643542643. The reversal of 643542637 is 736245346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 491908041 + 151634596 = 22179^2 + 12314^2 .

It is a cyclic number.

It is not a de Polignac number, because 643542637 - 2³ = 643542629 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643542637.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643542607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321771318 + 321771319.

It is an arithmetic number, because the mean of its divisors is an integer number (321771319).

Almost surely, 2^643542637 is an apocalyptic number.

It is an amenable number.

643542637 is a deficient number, since it is larger than the sum of its proper divisors (1).

643542637 is an equidigital number, since it uses as much as digits as its factorization.

643542637 is an evil number, because the sum of its binary digits is even.

The product of its digits is 362880, while the sum is 40.

The square root of 643542637 is about 25368.1421668990. The cubic root of 643542637 is about 863.3610302860.

The spelling of 643542637 in words is "six hundred forty-three million, five hundred forty-two thousand, six hundred thirty-seven".