2100661 has 2 divisors, whose sum is σ = 2100662. Its totient is φ = 2100660.

The previous prime is 2100649. The next prime is 2100691. The reversal of 2100661 is 1660012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2047761 + 52900 = 1431^2 + 230^2 .

It is a cyclic number.

It is not a de Polignac number, because 2100661 - 2⁵ = 2100629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2100691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1050330 + 1050331.

It is an arithmetic number, because the mean of its divisors is an integer number (1050331).

2^2100661 is an apocalyptic number.

It is an amenable number.

2100661 is a deficient number, since it is larger than the sum of its proper divisors (1).

2100661 is an equidigital number, since it uses as much as digits as its factorization.

2100661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 2100661 is about 1449.3657233425. The cubic root of 2100661 is about 128.0713510072.

Adding to 2100661 its reverse (1660012), we get a palindrome (3760673).

The spelling of 2100661 in words is "two million, one hundred thousand, six hundred sixty-one".