1664385521 has 2 divisors, whose sum is σ = 1664385522. Its totient is φ = 1664385520.

The previous prime is 1664385517. The next prime is 1664385533. The reversal of 1664385521 is 1255834661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1662600625 + 1784896 = 40775^2 + 1336^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664385521 - 2² = 1664385517 is a prime.

It is not a weakly prime, because it can be changed into another prime (1664385551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832192760 + 832192761.

It is an arithmetic number, because the mean of its divisors is an integer number (832192761).

Almost surely, 2^1664385521 is an apocalyptic number.

It is an amenable number.

1664385521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664385521 is an equidigital number, since it uses as much as digits as its factorization.

1664385521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 172800, while the sum is 41.

The square root of 1664385521 is about 40796.8812656066. The cubic root of 1664385521 is about 1185.0899350758.

The spelling of 1664385521 in words is "one billion, six hundred sixty-four million, three hundred eighty-five thousand, five hundred twenty-one".