643550 has 24 divisors (see below), whose sum is σ = 1222392. Its totient is φ = 252000.

The previous prime is 643547. The next prime is 643553. The reversal of 643550 is 55346.

Added to its reverse (55346) it gives a square (698896 = 836²).

It is an interprime number because it is at equal distance from previous prime (643547) and next prime (643553).

It is a Smith number, since the sum of its digits (23) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

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 polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2945 + ... + 3155.

It is an arithmetic number, because the mean of its divisors is an integer number (50933).

2⁶⁴³⁵⁵⁰ is an apocalyptic number.

643550 is a deficient number, since it is larger than the sum of its proper divisors (578842).

643550 is a wasteful number, since it uses less digits than its factorization.

643550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 284 (or 279 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 23.

The square root of 643550 is about 802.2156817216. The cubic root of 643550 is about 86.3364322947.

Adding to 643550 its reverse (55346), we get a palindrome (698896).

The spelling of 643550 in words is "six hundred forty-three thousand, five hundred fifty".