66405721549 has 2 divisors, whose sum is σ = 66405721550. Its totient is φ = 66405721548.

The previous prime is 66405721541. The next prime is 66405721583. The reversal of 66405721549 is 94512750466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 44165964649 + 22239756900 = 210157^2 + 149130^2 .

It is a cyclic number.

It is not a de Polignac number, because 66405721549 - 2³ = 66405721541 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66405721541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33202860774 + 33202860775.

It is an arithmetic number, because the mean of its divisors is an integer number (33202860775).

Almost surely, 2^66405721549 is an apocalyptic number.

It is an amenable number.

66405721549 is a deficient number, since it is larger than the sum of its proper divisors (1).

66405721549 is an equidigital number, since it uses as much as digits as its factorization.

66405721549 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1814400, while the sum is 49.

The spelling of 66405721549 in words is "sixty-six billion, four hundred five million, seven hundred twenty-one thousand, five hundred forty-nine".