125821781 has 4 divisors (see below), whose sum is σ = 132444000. Its totient is φ = 119199564.

The previous prime is 125821763. The next prime is 125821783. The reversal of 125821781 is 187128521.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-125821781 is a prime.

It is a super-2 number, since 2×125821781² = 31662241148023922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (125821783) 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, 3311081 + ... + 3311118.

It is an arithmetic number, because the mean of its divisors is an integer number (33111000).

Almost surely, 2^125821781 is an apocalyptic number.

It is an amenable number.

125821781 is a deficient number, since it is larger than the sum of its proper divisors (6622219).

125821781 is an equidigital number, since it uses as much as digits as its factorization.

125821781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6622218.

The product of its digits is 8960, while the sum is 35.

The square root of 125821781 is about 11217.0308459949. The cubic root of 125821781 is about 501.0933155796.

The spelling of 125821781 in words is "one hundred twenty-five million, eight hundred twenty-one thousand, seven hundred eighty-one".