1660706721 has 18 divisors (see below), whose sum is σ = 2484379430. Its totient is φ = 1068955776.

The previous prime is 1660706633. The next prime is 1660706731. The reversal of 1660706721 is 1276070661.

It can be written as a sum of positive squares in 3 ways, for example, as 390497121 + 1270209600 = 19761^2 + 35640^2 .

It is not a de Polignac number, because 1660706721 - 2¹⁷ = 1660575649 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1660706731) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 102136 + ... + 117273.

Almost surely, 2^1660706721 is an apocalyptic number.

It is an amenable number.

1660706721 is a deficient number, since it is larger than the sum of its proper divisors (823672709).

1660706721 is a wasteful number, since it uses less digits than its factorization.

1660706721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219473 (or 219441 counting only the distinct ones).

The product of its (nonzero) digits is 21168, while the sum is 36.

The square root of 1660706721 is about 40751.7695444014. The cubic root of 1660706721 is about 1184.2161541630.

The spelling of 1660706721 in words is "one billion, six hundred sixty million, seven hundred six thousand, seven hundred twenty-one".