163765261981 has 2 divisors, whose sum is σ = 163765261982. Its totient is φ = 163765261980.

The previous prime is 163765261949. The next prime is 163765261991. The reversal of 163765261981 is 189162567361.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 141673196025 + 22092065956 = 376395^2 + 148634^2 .

It is a cyclic number.

It is not a de Polignac number, because 163765261981 - 2⁵ = 163765261949 is a prime.

It is a super-2 number, since 2×163765261981² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (163765261901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 81882630990 + 81882630991.

It is an arithmetic number, because the mean of its divisors is an integer number (81882630991).

Almost surely, 2^163765261981 is an apocalyptic number.

It is an amenable number.

163765261981 is a deficient number, since it is larger than the sum of its proper divisors (1).

163765261981 is an equidigital number, since it uses as much as digits as its factorization.

163765261981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3265920, while the sum is 55.

The spelling of 163765261981 in words is "one hundred sixty-three billion, seven hundred sixty-five million, two hundred sixty-one thousand, nine hundred eighty-one".