643021749 has 6 divisors (see below), whose sum is σ = 928809206. Its totient is φ = 428681160.

The previous prime is 643021739. The next prime is 643021759. The reversal of 643021749 is 947120346.

643021749 is a `hidden beast` number, since 6 + 430 + 217 + 4 + 9 = 666.

It is an interprime number because it is at equal distance from previous prime (643021739) and next prime (643021759).

It can be written as a sum of positive squares in only one way, i.e., 492174225 + 150847524 = 22185^2 + 12282^2 .

It is not a de Polignac number, because 643021749 - 2¹⁵ = 642988981 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643021739) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35723422 + ... + 35723439.

Almost surely, 2^643021749 is an apocalyptic number.

It is an amenable number.

643021749 is a deficient number, since it is larger than the sum of its proper divisors (285787457).

643021749 is a wasteful number, since it uses less digits than its factorization.

643021749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71446867 (or 71446864 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 36.

The square root of 643021749 is about 25357.8735110025. The cubic root of 643021749 is about 863.1280305524.

The spelling of 643021749 in words is "six hundred forty-three million, twenty-one thousand, seven hundred forty-nine".