127640551721 has 4 divisors (see below), whose sum is σ = 129733019844. Its totient is φ = 125548083600.

The previous prime is 127640551711. The next prime is 127640551723. The reversal of 127640551721 is 127155046721.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 127155046721 = 71 ⋅1790916151.

It can be written as a sum of positive squares in 2 ways, for example, as 4779786496 + 122860765225 = 69136^2 + 350515^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-127640551721 is a prime.

It is a super-2 number, since 2×127640551721² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (127640551723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1046233970 + ... + 1046234091.

It is an arithmetic number, because the mean of its divisors is an integer number (32433254961).

Almost surely, 2^127640551721 is an apocalyptic number.

It is an amenable number.

127640551721 is a deficient number, since it is larger than the sum of its proper divisors (2092468123).

127640551721 is an equidigital number, since it uses as much as digits as its factorization.

127640551721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2092468122.

The product of its (nonzero) digits is 117600, while the sum is 41.

The spelling of 127640551721 in words is "one hundred twenty-seven billion, six hundred forty million, five hundred fifty-one thousand, seven hundred twenty-one".