666521437 has 2 divisors, whose sum is σ = 666521438. Its totient is φ = 666521436.

The previous prime is 666521423. The next prime is 666521467. The reversal of 666521437 is 734125666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 373803556 + 292717881 = 19334^2 + 17109^2 .

It is a cyclic number.

It is not a de Polignac number, because 666521437 - 2⁷ = 666521309 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 666521437.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666521467) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333260718 + 333260719.

It is an arithmetic number, because the mean of its divisors is an integer number (333260719).

Almost surely, 2^666521437 is an apocalyptic number.

It is an amenable number.

666521437 is a deficient number, since it is larger than the sum of its proper divisors (1).

666521437 is an equidigital number, since it uses as much as digits as its factorization.

666521437 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 181440, while the sum is 40.

The square root of 666521437 is about 25817.0764611332. The cubic root of 666521437 is about 873.5170252296.

The spelling of 666521437 in words is "six hundred sixty-six million, five hundred twenty-one thousand, four hundred thirty-seven".