166261261787 has 4 divisors (see below), whose sum is σ = 166263046656. Its totient is φ = 166259476920.

The previous prime is 166261261769. The next prime is 166261261843. The reversal of 166261261787 is 787162162661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 787162162661 = 7 ⋅112451737523.

It is a cyclic number.

It is not a de Polignac number, because 166261261787 - 2³² = 161966294491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166261261487) 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, 744539 + ... + 941732.

It is an arithmetic number, because the mean of its divisors is an integer number (41565761664).

Almost surely, 2^166261261787 is an apocalyptic number.

166261261787 is a deficient number, since it is larger than the sum of its proper divisors (1784869).

166261261787 is an equidigital number, since it uses as much as digits as its factorization.

166261261787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1784868.

The product of its digits is 2032128, while the sum is 53.

The spelling of 166261261787 in words is "one hundred sixty-six billion, two hundred sixty-one million, two hundred sixty-one thousand, seven hundred eighty-seven".