1820018561 has 4 divisors (see below), whose sum is σ = 1822331952. Its totient is φ = 1817705172.

The previous prime is 1820018539. The next prime is 1820018591. The reversal of 1820018561 is 1658100281.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1658100281 = 139 ⋅11928779.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1820018561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1820018591) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1155515 + ... + 1157088.

It is an arithmetic number, because the mean of its divisors is an integer number (455582988).

Almost surely, 2^1820018561 is an apocalyptic number.

It is an amenable number.

1820018561 is a deficient number, since it is larger than the sum of its proper divisors (2313391).

1820018561 is an equidigital number, since it uses as much as digits as its factorization.

1820018561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2313390.

The product of its (nonzero) digits is 3840, while the sum is 32.

The square root of 1820018561 is about 42661.6755531238. The cubic root of 1820018561 is about 1220.9333002210.

The spelling of 1820018561 in words is "one billion, eight hundred twenty million, eighteen thousand, five hundred sixty-one".