251661771157 has 4 divisors (see below), whose sum is σ = 251929212876. Its totient is φ = 251394329440.

The previous prime is 251661771029. The next prime is 251661771173. The reversal of 251661771157 is 751177166152.

251661771157 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 194793353316 + 56868417841 = 441354^2 + 238471^2 .

It is a cyclic number.

It is not a de Polignac number, because 251661771157 - 2⁷ = 251661771029 is a prime.

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 251661771157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251661772157) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133719448 + ... + 133721329.

It is an arithmetic number, because the mean of its divisors is an integer number (62982303219).

Almost surely, 2^251661771157 is an apocalyptic number.

It is an amenable number.

251661771157 is a deficient number, since it is larger than the sum of its proper divisors (267441719).

251661771157 is an equidigital number, since it uses as much as digits as its factorization.

251661771157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267441718.

The product of its digits is 617400, while the sum is 49.

The spelling of 251661771157 in words is "two hundred fifty-one billion, six hundred sixty-one million, seven hundred seventy-one thousand, one hundred fifty-seven".