643778953 has 4 divisors (see below), whose sum is σ = 664546048. Its totient is φ = 623011860.

The previous prime is 643778951. The next prime is 643778999. The reversal of 643778953 is 359877346.

It is a happy number.

643778953 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 643778953 - 2¹ = 643778951 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643778953.

It is not an unprimeable number, because it can be changed into a prime (643778951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10383501 + ... + 10383562.

It is an arithmetic number, because the mean of its divisors is an integer number (166136512).

Almost surely, 2^643778953 is an apocalyptic number.

It is an amenable number.

643778953 is a deficient number, since it is larger than the sum of its proper divisors (20767095).

643778953 is a wasteful number, since it uses less digits than its factorization.

643778953 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20767094.

The product of its digits is 3810240, while the sum is 52.

The square root of 643778953 is about 25372.7994710871. The cubic root of 643778953 is about 863.4666959379.

The spelling of 643778953 in words is "six hundred forty-three million, seven hundred seventy-eight thousand, nine hundred fifty-three".