643951 has 8 divisors (see below), whose sum is σ = 802944. Its totient is φ = 501720.

The previous prime is 643949. The next prime is 643957. The reversal of 643951 is 159346.

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 643951 - 2¹ = 643949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643957) 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 7 ways as a sum of consecutive naturals, for example, 4105 + ... + 4258.

It is an arithmetic number, because the mean of its divisors is an integer number (100368).

2⁶⁴³⁹⁵¹ is an apocalyptic number.

643951 is a deficient number, since it is larger than the sum of its proper divisors (158993).

643951 is a wasteful number, since it uses less digits than its factorization.

643951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8381.

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

The square root of 643951 is about 802.4655755856. The cubic root of 643951 is about 86.3543608271.

The spelling of 643951 in words is "six hundred forty-three thousand, nine hundred fifty-one".