1665677516981 has 2 divisors, whose sum is σ = 1665677516982. Its totient is φ = 1665677516980.

The previous prime is 1665677516843. The next prime is 1665677516989. The reversal of 1665677516981 is 1896157765661.

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., 1337182325956 + 328495191025 = 1156366^2 + 573145^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665677516981 - 2¹⁸ = 1665677254837 is a prime.

It is a super-2 number, since 2×1665677516981² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665677516989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832838758490 + 832838758491.

It is an arithmetic number, because the mean of its divisors is an integer number (832838758491).

Almost surely, 2^{1665677516981} is an apocalyptic number.

It is an amenable number.

1665677516981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665677516981 is an equidigital number, since it uses as much as digits as its factorization.

1665677516981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 114307200, while the sum is 68.

The spelling of 1665677516981 in words is "one trillion, six hundred sixty-five billion, six hundred seventy-seven million, five hundred sixteen thousand, nine hundred eighty-one".