2661821 has 2 divisors, whose sum is σ = 2661822. Its totient is φ = 2661820.

The previous prime is 2661797. The next prime is 2661833. The reversal of 2661821 is 1281662.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2524921 + 136900 = 1589^2 + 370^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2661821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2661871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330910 + 1330911.

It is an arithmetic number, because the mean of its divisors is an integer number (1330911).

2^2661821 is an apocalyptic number.

It is an amenable number.

2661821 is a deficient number, since it is larger than the sum of its proper divisors (1).

2661821 is an equidigital number, since it uses as much as digits as its factorization.

2661821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1152, while the sum is 26.

The square root of 2661821 is about 1631.5088108864. The cubic root of 2661821 is about 138.5882090019.

The spelling of 2661821 in words is "two million, six hundred sixty-one thousand, eight hundred twenty-one".