1665317281 has 2 divisors, whose sum is σ = 1665317282. Its totient is φ = 1665317280.

The previous prime is 1665317233. The next prime is 1665317309. The reversal of 1665317281 is 1827135661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1482635025 + 182682256 = 38505^2 + 13516^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665317281 - 2¹⁵ = 1665284513 is a prime.

It is a super-2 number, since 2×1665317281² = 5546563292794465922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1665317881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832658640 + 832658641.

It is an arithmetic number, because the mean of its divisors is an integer number (832658641).

Almost surely, 2^1665317281 is an apocalyptic number.

It is an amenable number.

1665317281 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665317281 is an equidigital number, since it uses as much as digits as its factorization.

1665317281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60480, while the sum is 40.

The square root of 1665317281 is about 40808.2991681839. The cubic root of 1665317281 is about 1185.3110403811.

The spelling of 1665317281 in words is "one billion, six hundred sixty-five million, three hundred seventeen thousand, two hundred eighty-one".