1811921521 has 2 divisors, whose sum is σ = 1811921522. Its totient is φ = 1811921520.

The previous prime is 1811921483. The next prime is 1811921563. The reversal of 1811921521 is 1251291181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1760641600 + 51279921 = 41960^2 + 7161^2 .

It is a cyclic number.

It is not a de Polignac number, because 1811921521 - 2⁹ = 1811921009 is a prime.

It is not a weakly prime, because it can be changed into another prime (1811921021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 905960760 + 905960761.

It is an arithmetic number, because the mean of its divisors is an integer number (905960761).

Almost surely, 2^1811921521 is an apocalyptic number.

It is an amenable number.

1811921521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1811921521 is an equidigital number, since it uses as much as digits as its factorization.

1811921521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1440, while the sum is 31.

The square root of 1811921521 is about 42566.6714813362. The cubic root of 1811921521 is about 1219.1200142141.

The spelling of 1811921521 in words is "one billion, eight hundred eleven million, nine hundred twenty-one thousand, five hundred twenty-one".