66405721613 has 16 divisors (see below), whose sum is σ = 82803517440. Its totient is φ = 51737238000.

The previous prime is 66405721597. The next prime is 66405721631. The reversal of 66405721613 is 31612750466.

It is not a de Polignac number, because 66405721613 - 2⁴ = 66405721597 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66405721663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 507368 + ... + 624686.

It is an arithmetic number, because the mean of its divisors is an integer number (5175219840).

Almost surely, 2^66405721613 is an apocalyptic number.

It is an amenable number.

66405721613 is a deficient number, since it is larger than the sum of its proper divisors (16397795827).

66405721613 is a wasteful number, since it uses less digits than its factorization.

66405721613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124688.

The product of its (nonzero) digits is 181440, while the sum is 41.

The spelling of 66405721613 in words is "sixty-six billion, four hundred five million, seven hundred twenty-one thousand, six hundred thirteen".