643579901 has 4 divisors (see below), whose sum is σ = 655722972. Its totient is φ = 631436832.

The previous prime is 643579889. The next prime is 643579903. The reversal of 643579901 is 109975346.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 588062500 + 55517401 = 24250^2 + 7451^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643579901 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 (643579903) 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, 6071456 + ... + 6071561.

It is an arithmetic number, because the mean of its divisors is an integer number (163930743).

Almost surely, 2^643579901 is an apocalyptic number.

It is an amenable number.

643579901 is a deficient number, since it is larger than the sum of its proper divisors (12143071).

643579901 is a wasteful number, since it uses less digits than its factorization.

643579901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12143070.

The product of its (nonzero) digits is 204120, while the sum is 44.

The square root of 643579901 is about 25368.8766207729. The cubic root of 643579901 is about 863.3776941208.

The spelling of 643579901 in words is "six hundred forty-three million, five hundred seventy-nine thousand, nine hundred one".