71389961721 has 135 divisors (see below), whose sum is σ = 122621132283. Its totient is φ = 40014224640.

The previous prime is 71389961683. The next prime is 71389961723. The reversal of 71389961721 is 12716998317.

It is a happy number.

The square root of 71389961721 is 267189.

It is a perfect power (a square), and thus also a powerful number.

71389961721 is a `hidden beast` number, since 7 + 1 + 389 + 96 + 172 + 1 = 666.

It can be written as a sum of positive squares in 7 ways, for example, as 65170431225 + 6219530496 = 255285^2 + 78864^2 .

It is not a de Polignac number, because 71389961721 - 2⁷ = 71389961593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (71389961723) by changing a digit.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 2302901976 + ... + 2302902006.

Almost surely, 2^71389961721 is an apocalyptic number.

71389961721 is the 267189-th square number.

71389961721 is the 133595-th centered octagonal number.

It is an amenable number.

71389961721 is a deficient number, since it is larger than the sum of its proper divisors (51231170562).

71389961721 is an equidigital number, since it uses as much as digits as its factorization.

71389961721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154 (or 64 counting only the distinct ones).

The product of its digits is 1143072, while the sum is 54.

The spelling of 71389961721 in words is "seventy-one billion, three hundred eighty-nine million, nine hundred sixty-one thousand, seven hundred twenty-one".