1985381621 has 2 divisors, whose sum is σ = 1985381622. Its totient is φ = 1985381620.

The previous prime is 1985381617. The next prime is 1985381659. The reversal of 1985381621 is 1261835891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1790220721 + 195160900 = 42311^2 + 13970^2 .

It is a cyclic number.

It is not a de Polignac number, because 1985381621 - 2² = 1985381617 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1985381521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 992690810 + 992690811.

It is an arithmetic number, because the mean of its divisors is an integer number (992690811).

Almost surely, 2^1985381621 is an apocalyptic number.

It is an amenable number.

1985381621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1985381621 is an equidigital number, since it uses as much as digits as its factorization.

1985381621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 103680, while the sum is 44.

The square root of 1985381621 is about 44557.6213570698. The cubic root of 1985381621 is about 1256.8438732140.

The spelling of 1985381621 in words is "one billion, nine hundred eighty-five million, three hundred eighty-one thousand, six hundred twenty-one".