646704181 has 2 divisors, whose sum is σ = 646704182. Its totient is φ = 646704180.

The previous prime is 646704173. The next prime is 646704187. The reversal of 646704181 is 181407646.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 574369156 + 72335025 = 23966^2 + 8505^2 .

It is a cyclic number.

It is not a de Polignac number, because 646704181 - 2³ = 646704173 is a prime.

It is a super-2 number, since 2×646704181² = 836452595445761522, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 646704181.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646704187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323352090 + 323352091.

It is an arithmetic number, because the mean of its divisors is an integer number (323352091).

Almost surely, 2^646704181 is an apocalyptic number.

It is an amenable number.

646704181 is a deficient number, since it is larger than the sum of its proper divisors (1).

646704181 is an equidigital number, since it uses as much as digits as its factorization.

646704181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32256, while the sum is 37.

The square root of 646704181 is about 25430.3790966631. The cubic root of 646704181 is about 864.7725380062.

The spelling of 646704181 in words is "six hundred forty-six million, seven hundred four thousand, one hundred eighty-one".