643915 has 8 divisors (see below), whose sum is σ = 781920. Its totient is φ = 508992.

The previous prime is 643889. The next prime is 643919. The reversal of 643915 is 519346.

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 643915 - 2⁵ = 643883 is a prime.

643915 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (643919) 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 7 ways as a sum of consecutive naturals, for example, 279 + ... + 1168.

It is an arithmetic number, because the mean of its divisors is an integer number (97740).

2⁶⁴³⁹¹⁵ is an apocalyptic number.

643915 is a deficient number, since it is larger than the sum of its proper divisors (138005).

643915 is a wasteful number, since it uses less digits than its factorization.

643915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1541.

The product of its digits is 3240, while the sum is 28.

The square root of 643915 is about 802.4431444034. The cubic root of 643915 is about 86.3527515872.

The spelling of 643915 in words is "six hundred forty-three thousand, nine hundred fifteen".