7725217721 has 8 divisors (see below), whose sum is σ = 8324857800. Its totient is φ = 7126348032.

The previous prime is 7725217697. The next prime is 7725217769. The reversal of 7725217721 is 1277125277.

It can be written as a sum of positive squares in 4 ways, for example, as 73342096 + 7651875625 = 8564^2 + 87475^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7725217721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7725217321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 171680 + ... + 211953.

It is an arithmetic number, because the mean of its divisors is an integer number (1040607225).

Almost surely, 2^7725217721 is an apocalyptic number.

It is an amenable number.

7725217721 is a deficient number, since it is larger than the sum of its proper divisors (599640079).

7725217721 is a wasteful number, since it uses less digits than its factorization.

7725217721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 385195.

The product of its digits is 96040, while the sum is 41.

The square root of 7725217721 is about 87893.2177190026. The cubic root of 7725217721 is about 1976.8341852680.

The spelling of 7725217721 in words is "seven billion, seven hundred twenty-five million, two hundred seventeen thousand, seven hundred twenty-one".