1815562561 has 2 divisors, whose sum is σ = 1815562562. Its totient is φ = 1815562560.

The previous prime is 1815562547. The next prime is 1815562621. The reversal of 1815562561 is 1652655181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1795132161 + 20430400 = 42369^2 + 4520^2 .

It is an emirp because it is prime and its reverse (1652655181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1815562561 - 2⁷ = 1815562433 is a prime.

It is not a weakly prime, because it can be changed into another prime (1815562961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 907781280 + 907781281.

It is an arithmetic number, because the mean of its divisors is an integer number (907781281).

Almost surely, 2^1815562561 is an apocalyptic number.

It is an amenable number.

1815562561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1815562561 is an equidigital number, since it uses as much as digits as its factorization.

1815562561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72000, while the sum is 40.

The square root of 1815562561 is about 42609.4186888298. The cubic root of 1815562561 is about 1219.9360714061.

The spelling of 1815562561 in words is "one billion, eight hundred fifteen million, five hundred sixty-two thousand, five hundred sixty-one".