646651691 has 4 divisors (see below), whose sum is σ = 739030512. Its totient is φ = 554272872.

The previous prime is 646651679. The next prime is 646651703. The reversal of 646651691 is 196156646.

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

It is an interprime number because it is at equal distance from previous prime (646651679) and next prime (646651703).

It is a cyclic number.

It is not a de Polignac number, because 646651691 - 2²⁶ = 579542827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646651651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46189400 + ... + 46189413.

It is an arithmetic number, because the mean of its divisors is an integer number (184757628).

Almost surely, 2^646651691 is an apocalyptic number.

646651691 is a deficient number, since it is larger than the sum of its proper divisors (92378821).

646651691 is an equidigital number, since it uses as much as digits as its factorization.

646651691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92378820.

The product of its digits is 233280, while the sum is 44.

The square root of 646651691 is about 25429.3470423446. The cubic root of 646651691 is about 864.7491408385.

The spelling of 646651691 in words is "six hundred forty-six million, six hundred fifty-one thousand, six hundred ninety-one".