656129891 has 4 divisors (see below), whose sum is σ = 656798352. Its totient is φ = 655461432.

The previous prime is 656129797. The next prime is 656129893. The reversal of 656129891 is 198921656.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-656129891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (656129893) 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, 332756 + ... + 334721.

It is an arithmetic number, because the mean of its divisors is an integer number (164199588).

Almost surely, 2^656129891 is an apocalyptic number.

656129891 is a deficient number, since it is larger than the sum of its proper divisors (668461).

656129891 is an equidigital number, since it uses as much as digits as its factorization.

656129891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668460.

The product of its digits is 233280, while the sum is 47.

The square root of 656129891 is about 25615.0325199872. The cubic root of 656129891 is about 868.9536418492.

The spelling of 656129891 in words is "six hundred fifty-six million, one hundred twenty-nine thousand, eight hundred ninety-one".