1006505665721 has 4 divisors (see below), whose sum is σ = 1008028367844. Its totient is φ = 1004982963600.

The previous prime is 1006505665699. The next prime is 1006505665729. The reversal of 1006505665721 is 1275665056001.

1006505665721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 824483976121 + 182021689600 = 908011^2 + 426640^2 .

It is a cyclic number.

It is not a de Polignac number, because 1006505665721 - 2³⁸ = 731627758777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1006505665729) 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, 761350070 + ... + 761351391.

It is an arithmetic number, because the mean of its divisors is an integer number (252007091961).

Almost surely, 2^{1006505665721} is an apocalyptic number.

It is an amenable number.

1006505665721 is a deficient number, since it is larger than the sum of its proper divisors (1522702123).

1006505665721 is an equidigital number, since it uses as much as digits as its factorization.

1006505665721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1522702122.

The product of its (nonzero) digits is 378000, while the sum is 44.

The spelling of 1006505665721 in words is "one trillion, six billion, five hundred five million, six hundred sixty-five thousand, seven hundred twenty-one".