71721997 has 12 divisors (see below), whose sum is σ = 78060276. Its totient is φ = 65845760.

The previous prime is 71721977. The next prime is 71722009. The reversal of 71721997 is 79912717.

It can be written as a sum of positive squares in 6 ways, for example, as 4137156 + 67584841 = 2034^2 + 8221^2 .

It is not a de Polignac number, because 71721997 - 2⁷ = 71721869 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71721907) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8823 + ... + 14875.

It is an arithmetic number, because the mean of its divisors is an integer number (6505023).

Almost surely, 2^71721997 is an apocalyptic number.

It is an amenable number.

71721997 is a deficient number, since it is larger than the sum of its proper divisors (6338279).

71721997 is a wasteful number, since it uses less digits than its factorization.

71721997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6128 (or 6111 counting only the distinct ones).

The product of its digits is 55566, while the sum is 43.

The square root of 71721997 is about 8468.8840469096. The cubic root of 71721997 is about 415.4806392344.

The spelling of 71721997 in words is "seventy-one million, seven hundred twenty-one thousand, nine hundred ninety-seven".