66720620051605 has 8 divisors (see below), whose sum is σ = 86223570528312. Its totient is φ = 49270611730368.

The previous prime is 66720620051599. The next prime is 66720620051681. The reversal of 66720620051605 is 50615002602766.

It can be written as a sum of positive squares in 4 ways, for example, as 4667850991441 + 62052769060164 = 2160521^2 + 7877358^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 66720620051605 - 2²³ = 66720611662997 is a prime.

It is a super-2 number, since 2×66720620051605² (a number of 28 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 513235538794 + ... + 513235538923.

It is an arithmetic number, because the mean of its divisors is an integer number (10777946316039).

Almost surely, 2^{66720620051605} is an apocalyptic number.

66720620051605 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

66720620051605 is a deficient number, since it is larger than the sum of its proper divisors (19502950476707).

66720620051605 is a wasteful number, since it uses less digits than its factorization.

66720620051605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1026471077735.

The product of its (nonzero) digits is 907200, while the sum is 46.

The spelling of 66720620051605 in words is "sixty-six trillion, seven hundred twenty billion, six hundred twenty million, fifty-one thousand, six hundred five".