643923 has 16 divisors (see below), whose sum is σ = 1090560. Its totient is φ = 367848.

The previous prime is 643919. The next prime is 643927. The reversal of 643923 is 329346.

It is an interprime number because it is at equal distance from previous prime (643919) and next prime (643927).

It is not a de Polignac number, because 643923 - 2² = 643919 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a d-powerful number, because it can be written as 6⁶ + 4⁸ + 9² + 3⁴ + 2⁷ + 3¹² .

643923 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (643927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1515 + ... + 1892.

It is an arithmetic number, because the mean of its divisors is an integer number (68160).

2⁶⁴³⁹²³ is an apocalyptic number.

643923 is a gapful number since it is divisible by the number (63) formed by its first and last digit.

643923 is a deficient number, since it is larger than the sum of its proper divisors (446637).

643923 is a wasteful number, since it uses less digits than its factorization.

643923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3423 (or 3417 counting only the distinct ones).

The product of its digits is 3888, while the sum is 27.

The square root of 643923 is about 802.4481291647. The cubic root of 643923 is about 86.3531092012.

The spelling of 643923 in words is "six hundred forty-three thousand, nine hundred twenty-three".