643551 has 4 divisors (see below), whose sum is σ = 858072. Its totient is φ = 429032.

The previous prime is 643547. The next prime is 643553. The reversal of 643551 is 155346.

643551 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643551 - 2² = 643547 is a prime.

It is a D-number.

643551 is strictly pandigital in base 7.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107256 + ... + 107261.

It is an arithmetic number, because the mean of its divisors is an integer number (214518).

2⁶⁴³⁵⁵¹ is an apocalyptic number.

643551 is a deficient number, since it is larger than the sum of its proper divisors (214521).

643551 is a wasteful number, since it uses less digits than its factorization.

643551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214520.

The product of its digits is 1800, while the sum is 24.

The square root of 643551 is about 802.2163049951. The cubic root of 643551 is about 86.3364770135.

Adding to 643551 its reverse (155346), we get a palindrome (798897).

The spelling of 643551 in words is "six hundred forty-three thousand, five hundred fifty-one".