664577666711521 has 4 divisors (see below), whose sum is σ = 664579653581844. Its totient is φ = 664575679841200.

The previous prime is 664577666711509. The next prime is 664577666711531. The reversal of 664577666711521 is 125117666775466.

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 496510296465121 + 168067370246400 = 22282511^2 + 12964080^2 .

It is a cyclic number.

It is not a de Polignac number, because 664577666711521 - 2³⁵ = 664543306973153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664577666711531) 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, 992933350 + ... + 993602431.

It is an arithmetic number, because the mean of its divisors is an integer number (166144913395461).

Almost surely, 2^{664577666711521} is an apocalyptic number.

It is an amenable number.

664577666711521 is a deficient number, since it is larger than the sum of its proper divisors (1986870323).

664577666711521 is a wasteful number, since it uses less digits than its factorization.

664577666711521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1986870322.

The product of its digits is 533433600, while the sum is 70.

The spelling of 664577666711521 in words is "six hundred sixty-four trillion, five hundred seventy-seven billion, six hundred sixty-six million, seven hundred eleven thousand, five hundred twenty-one".