656291991 has 8 divisors (see below), whose sum is σ = 875745280. Its totient is φ = 437183352.

The previous prime is 656291971. The next prime is 656292017. The reversal of 656291991 is 199192656.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 656291991 - 2⁹ = 656291479 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 656291991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656291921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 81685 + ... + 89358.

It is an arithmetic number, because the mean of its divisors is an integer number (109468160).

Almost surely, 2^656291991 is an apocalyptic number.

656291991 is a deficient number, since it is larger than the sum of its proper divisors (219453289).

656291991 is a wasteful number, since it uses less digits than its factorization.

656291991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172325.

The product of its digits is 262440, while the sum is 48.

The square root of 656291991 is about 25618.1964821882. The cubic root of 656291991 is about 869.0251956625.

The spelling of 656291991 in words is "six hundred fifty-six million, two hundred ninety-one thousand, nine hundred ninety-one".