17256721261 has 4 divisors (see below), whose sum is σ = 18584161372. Its totient is φ = 15929281152.

The previous prime is 17256721247. The next prime is 17256721277. The reversal of 17256721261 is 16212765271.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5945335236 + 11311386025 = 77106^2 + 106355^2 .

It is a cyclic number.

It is not a de Polignac number, because 17256721261 - 2⁷ = 17256721133 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 (17256721231) 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, 663720036 + ... + 663720061.

It is an arithmetic number, because the mean of its divisors is an integer number (4646040343).

Almost surely, 2^17256721261 is an apocalyptic number.

It is an amenable number.

17256721261 is a deficient number, since it is larger than the sum of its proper divisors (1327440111).

17256721261 is a wasteful number, since it uses less digits than its factorization.

17256721261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1327440110.

The product of its digits is 70560, while the sum is 40.

The spelling of 17256721261 in words is "seventeen billion, two hundred fifty-six million, seven hundred twenty-one thousand, two hundred sixty-one".