2001781601 has 2 divisors, whose sum is σ = 2001781602. Its totient is φ = 2001781600.

The previous prime is 2001781591. The next prime is 2001781679. The reversal of 2001781601 is 1061871002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1682230225 + 319551376 = 41015^2 + 17876^2 .

It is a cyclic number.

It is not a de Polignac number, because 2001781601 - 2¹⁴ = 2001765217 is a prime.

It is not a weakly prime, because it can be changed into another prime (2001711601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1000890800 + 1000890801.

It is an arithmetic number, because the mean of its divisors is an integer number (1000890801).

Almost surely, 2^2001781601 is an apocalyptic number.

It is an amenable number.

2001781601 is a deficient number, since it is larger than the sum of its proper divisors (1).

2001781601 is an equidigital number, since it uses as much as digits as its factorization.

2001781601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 672, while the sum is 26.

The square root of 2001781601 is about 44741.2740207518. The cubic root of 2001781601 is about 1260.2950516303.

The spelling of 2001781601 in words is "two billion, one million, seven hundred eighty-one thousand, six hundred one".