643789129 has 3 divisors (see below), whose sum is σ = 643814503. Its totient is φ = 643763756.

The previous prime is 643789123. The next prime is 643789171. The reversal of 643789129 is 921987346.

The square root of 643789129 is 25373.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 6125625 + 637663504 = 2475^2 + 25252^2 .

It is a de Polignac number, because none of the positive numbers 2^k-643789129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643789123) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 12687 + ... + 38059.

Almost surely, 2^643789129 is an apocalyptic number.

643789129 is the 25373-rd square number.

643789129 is the 12687-th centered octagonal number.

It is an amenable number.

643789129 is a deficient number, since it is larger than the sum of its proper divisors (25374).

643789129 is an frugal number, since it uses more digits than its factorization.

643789129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50746 (or 25373 counting only the distinct ones).

The product of its digits is 653184, while the sum is 49.

The cubic root of 643789129 is about 863.4712454243.

Multiplying 643789129 by its sum of digits (49), we get a square (31545667321 = 177611²).

The spelling of 643789129 in words is "six hundred forty-three million, seven hundred eighty-nine thousand, one hundred twenty-nine".