1664871521 has 2 divisors, whose sum is σ = 1664871522. Its totient is φ = 1664871520.

The previous prime is 1664871497. The next prime is 1664871589. The reversal of 1664871521 is 1251784661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1622478400 + 42393121 = 40280^2 + 6511^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1664871521 is a prime.

It is not a weakly prime, because it can be changed into another prime (1664870521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832435760 + 832435761.

It is an arithmetic number, because the mean of its divisors is an integer number (832435761).

Almost surely, 2^1664871521 is an apocalyptic number.

It is an amenable number.

1664871521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664871521 is an equidigital number, since it uses as much as digits as its factorization.

1664871521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80640, while the sum is 41.

The square root of 1664871521 is about 40802.8371685107. The cubic root of 1664871521 is about 1185.2052724682.

The spelling of 1664871521 in words is "one billion, six hundred sixty-four million, eight hundred seventy-one thousand, five hundred twenty-one".