125916686521 has 4 divisors (see below), whose sum is σ = 133323550452. Its totient is φ = 118509822592.

The previous prime is 125916686501. The next prime is 125916686543. The reversal of 125916686521 is 125686619521.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 125686619521 = 4241 ⋅29636081.

It can be written as a sum of positive squares in 2 ways, for example, as 110968934400 + 14947752121 = 333120^2 + 122261^2 .

It is a cyclic number.

It is not a de Polignac number, because 125916686521 - 2⁹ = 125916686009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (125916686501) 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, 3703431940 + ... + 3703431973.

It is an arithmetic number, because the mean of its divisors is an integer number (33330887613).

Almost surely, 2^125916686521 is an apocalyptic number.

It is an amenable number.

125916686521 is a deficient number, since it is larger than the sum of its proper divisors (7406863931).

125916686521 is an equidigital number, since it uses as much as digits as its factorization.

125916686521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7406863930.

The product of its digits is 1555200, while the sum is 52.

The spelling of 125916686521 in words is "one hundred twenty-five billion, nine hundred sixteen million, six hundred eighty-six thousand, five hundred twenty-one".