8251242721 has 2 divisors, whose sum is σ = 8251242722. Its totient is φ = 8251242720.

The previous prime is 8251242707. The next prime is 8251242739. The reversal of 8251242721 is 1272421528.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8249180625 + 2062096 = 90825^2 + 1436^2 .

It is a cyclic number.

It is not a de Polignac number, because 8251242721 - 2¹⁹ = 8250718433 is a prime.

It is not a weakly prime, because it can be changed into another prime (8251242761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4125621360 + 4125621361.

It is an arithmetic number, because the mean of its divisors is an integer number (4125621361).

Almost surely, 2^8251242721 is an apocalyptic number.

It is an amenable number.

8251242721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8251242721 is an equidigital number, since it uses as much as digits as its factorization.

8251242721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17920, while the sum is 34.

The square root of 8251242721 is about 90836.3513192819. The cubic root of 8251242721 is about 2020.7214624665.

The spelling of 8251242721 in words is "eight billion, two hundred fifty-one million, two hundred forty-two thousand, seven hundred twenty-one".