64540561 has 4 divisors (see below), whose sum is σ = 64640052. Its totient is φ = 64441072.

The previous prime is 64540559. The next prime is 64540577. The reversal of 64540561 is 16504546.

64540561 = T₆₅₅₈ + T₆₅₅₉ + T₆₅₆₀.

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 38987536 + 25553025 = 6244^2 + 5055^2 .

It is a cyclic number.

It is not a de Polignac number, because 64540561 - 2¹ = 64540559 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is not an unprimeable number, because it can be changed into a prime (64540961) 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, 48766 + ... + 50071.

It is an arithmetic number, because the mean of its divisors is an integer number (16160013).

Almost surely, 2^64540561 is an apocalyptic number.

64540561 is the 6560-th centered triangular number.

It is an amenable number.

64540561 is a deficient number, since it is larger than the sum of its proper divisors (99491).

64540561 is an equidigital number, since it uses as much as digits as its factorization.

64540561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99490.

The product of its (nonzero) digits is 14400, while the sum is 31.

The square root of 64540561 is about 8033.7140227917. The cubic root of 64540561 is about 401.1230129044.

The spelling of 64540561 in words is "sixty-four million, five hundred forty thousand, five hundred sixty-one".