64991209 has 4 divisors (see below), whose sum is σ = 65213316. Its totient is φ = 64769104.

The previous prime is 64991161. The next prime is 64991219. The reversal of 64991209 is 90219946.

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 44515584 + 20475625 = 6672^2 + 4525^2 .

It is a cyclic number.

It is not a de Polignac number, because 64991209 - 2¹¹ = 64989161 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (64991219) 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, 110614 + ... + 111199.

It is an arithmetic number, because the mean of its divisors is an integer number (16303329).

Almost surely, 2^64991209 is an apocalyptic number.

It is an amenable number.

64991209 is a deficient number, since it is larger than the sum of its proper divisors (222107).

64991209 is a wasteful number, since it uses less digits than its factorization.

64991209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 222106.

The product of its (nonzero) digits is 34992, while the sum is 40.

The square root of 64991209 is about 8061.7125351875. The cubic root of 64991209 is about 402.0544487852.

The spelling of 64991209 in words is "sixty-four million, nine hundred ninety-one thousand, two hundred nine".