125691681 has 4 divisors (see below), whose sum is σ = 167588912. Its totient is φ = 83794452.

The previous prime is 125691641. The next prime is 125691703. The reversal of 125691681 is 186196521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 125691681 - 2⁹ = 125691169 is a prime.

It is a super-2 number, since 2×125691681² = 31596797345211522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (125691611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20948611 + ... + 20948616.

It is an arithmetic number, because the mean of its divisors is an integer number (41897228).

Almost surely, 2^125691681 is an apocalyptic number.

It is an amenable number.

125691681 is a deficient number, since it is larger than the sum of its proper divisors (41897231).

125691681 is an equidigital number, since it uses as much as digits as its factorization.

125691681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41897230.

The product of its digits is 25920, while the sum is 39.

The square root of 125691681 is about 11211.2301287593. The cubic root of 125691681 is about 500.9205454853.

The spelling of 125691681 in words is "one hundred twenty-five million, six hundred ninety-one thousand, six hundred eighty-one".