1661665001 has 2 divisors, whose sum is σ = 1661665002. Its totient is φ = 1661665000.

The previous prime is 1661664989. The next prime is 1661665087. The reversal of 1661665001 is 1005661661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1505440000 + 156225001 = 38800^2 + 12499^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661665001 - 2⁶ = 1661664937 is a prime.

It is a super-2 number, since 2×1661665001² = 5522261151096660002, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1661665601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830832500 + 830832501.

It is an arithmetic number, because the mean of its divisors is an integer number (830832501).

Almost surely, 2^1661665001 is an apocalyptic number.

It is an amenable number.

1661665001 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661665001 is an equidigital number, since it uses as much as digits as its factorization.

1661665001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 1661665001 is about 40763.5253750212. The cubic root of 1661665001 is about 1184.4438870188.

The spelling of 1661665001 in words is "one billion, six hundred sixty-one million, six hundred sixty-five thousand, one".