1665639749 has 2 divisors, whose sum is σ = 1665639750. Its totient is φ = 1665639748.

The previous prime is 1665639727. The next prime is 1665639761. The reversal of 1665639749 is 9479365661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1556854849 + 108784900 = 39457^2 + 10430^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665639749 - 2²⁴ = 1648862533 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1665639694 and 1665639703.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665639049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832819874 + 832819875.

It is an arithmetic number, because the mean of its divisors is an integer number (832819875).

Almost surely, 2^1665639749 is an apocalyptic number.

It is an amenable number.

1665639749 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665639749 is an equidigital number, since it uses as much as digits as its factorization.

1665639749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7348320, while the sum is 56.

The square root of 1665639749 is about 40812.2499869831. The cubic root of 1665639749 is about 1185.3875423619.

The spelling of 1665639749 in words is "one billion, six hundred sixty-five million, six hundred thirty-nine thousand, seven hundred forty-nine".