1891530821 has 2 divisors, whose sum is σ = 1891530822. Its totient is φ = 1891530820.

The previous prime is 1891530799. The next prime is 1891530841. The reversal of 1891530821 is 1280351981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1779996100 + 111534721 = 42190^2 + 10561^2 .

It is a cyclic number.

It is not a de Polignac number, because 1891530821 - 2⁶ = 1891530757 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1891530841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 945765410 + 945765411.

It is an arithmetic number, because the mean of its divisors is an integer number (945765411).

Almost surely, 2^1891530821 is an apocalyptic number.

It is an amenable number.

1891530821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1891530821 is an equidigital number, since it uses as much as digits as its factorization.

1891530821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17280, while the sum is 38.

The square root of 1891530821 is about 43491.7327891175. The cubic root of 1891530821 is about 1236.7193067426.

The spelling of 1891530821 in words is "one billion, eight hundred ninety-one million, five hundred thirty thousand, eight hundred twenty-one".