166774887781 has 4 divisors (see below), whose sum is σ = 166775719500. Its totient is φ = 166774056064.

The previous prime is 166774887757. The next prime is 166774887793. The reversal of 166774887781 is 187788477661.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 187788477661 = 49807 ⋅3770323.

It can be written as a sum of positive squares in 2 ways, for example, as 147233364100 + 19541523681 = 383710^2 + 139791^2 .

It is a cyclic number.

It is not a de Polignac number, because 166774887781 - 2⁹ = 166774887269 is a prime.

It is a super-2 number, since 2×166774887781² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 166774887781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166774881781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 90165 + ... + 584533.

It is an arithmetic number, because the mean of its divisors is an integer number (41693929875).

Almost surely, 2^166774887781 is an apocalyptic number.

It is an amenable number.

166774887781 is a deficient number, since it is larger than the sum of its proper divisors (831719).

166774887781 is an equidigital number, since it uses as much as digits as its factorization.

166774887781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 831718.

The product of its digits is 177020928, while the sum is 70.

The spelling of 166774887781 in words is "one hundred sixty-six billion, seven hundred seventy-four million, eight hundred eighty-seven thousand, seven hundred eighty-one".