1827721661 has 2 divisors, whose sum is σ = 1827721662. Its totient is φ = 1827721660.

The previous prime is 1827721639. The next prime is 1827721673. The reversal of 1827721661 is 1661277281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1584517636 + 243204025 = 39806^2 + 15595^2 .

It is a cyclic number.

It is not a de Polignac number, because 1827721661 - 2¹⁴ = 1827705277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1827721601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 913860830 + 913860831.

It is an arithmetic number, because the mean of its divisors is an integer number (913860831).

Almost surely, 2^1827721661 is an apocalyptic number.

It is an amenable number.

1827721661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1827721661 is an equidigital number, since it uses as much as digits as its factorization.

1827721661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56448, while the sum is 41.

The square root of 1827721661 is about 42751.8614916357. The cubic root of 1827721661 is about 1222.6533804428.

The spelling of 1827721661 in words is "one billion, eight hundred twenty-seven million, seven hundred twenty-one thousand, six hundred sixty-one".