643775551 has 8 divisors (see below), whose sum is σ = 648019008. Its totient is φ = 639540000.

The previous prime is 643775549. The next prime is 643775569. The reversal of 643775551 is 155577346.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 643775551 - 2¹ = 643775549 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643775498 and 643775507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643775051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 337701 + ... + 339601.

It is an arithmetic number, because the mean of its divisors is an integer number (81002376).

Almost surely, 2^643775551 is an apocalyptic number.

643775551 is a deficient number, since it is larger than the sum of its proper divisors (4243457).

643775551 is a wasteful number, since it uses less digits than its factorization.

643775551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3953.

The product of its digits is 441000, while the sum is 43.

The square root of 643775551 is about 25372.7324307021. The cubic root of 643775551 is about 863.4651749609.

The spelling of 643775551 in words is "six hundred forty-three million, seven hundred seventy-five thousand, five hundred fifty-one".