643890 has 48 divisors (see below), whose sum is σ = 1686528. Its totient is φ = 157248.

The previous prime is 643889. The next prime is 643919. The reversal of 643890 is 98346.

643890 = T₁₀₇ + T₁₀₈ + ... + T₁₇₁.

643890 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5007 + ... + 5133.

It is an arithmetic number, because the mean of its divisors is an integer number (35136).

2⁶⁴³⁸⁹⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (843264).

643890 is an abundant number, since it is smaller than the sum of its proper divisors (1042638).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643890 is a wasteful number, since it uses less digits than its factorization.

643890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163 (or 150 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 643890 is about 802.4275668246. The cubic root of 643890 is about 86.3516340242.

The spelling of 643890 in words is "six hundred forty-three thousand, eight hundred ninety".