157681561 has 4 divisors (see below), whose sum is σ = 157708900. Its totient is φ = 157654224.

The previous prime is 157681547. The next prime is 157681591. The reversal of 157681561 is 165186751.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165186751 = 383 ⋅431297.

It can be written as a sum of positive squares in 2 ways, for example, as 152646025 + 5035536 = 12355^2 + 2244^2 .

It is a cyclic number.

It is not a de Polignac number, because 157681561 - 2⁵ = 157681529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (157681501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1266 + ... + 17803.

It is an arithmetic number, because the mean of its divisors is an integer number (39427225).

Almost surely, 2^157681561 is an apocalyptic number.

It is an amenable number.

157681561 is a deficient number, since it is larger than the sum of its proper divisors (27339).

157681561 is an equidigital number, since it uses as much as digits as its factorization.

157681561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27338.

The product of its digits is 50400, while the sum is 40.

The square root of 157681561 is about 12557.1318779409. The cubic root of 157681561 is about 540.2485835376.

The spelling of 157681561 in words is "one hundred fifty-seven million, six hundred eighty-one thousand, five hundred sixty-one".