1821988081 has 4 divisors (see below), whose sum is σ = 1831144000. Its totient is φ = 1812832164.

The previous prime is 1821988057. The next prime is 1821988099. The reversal of 1821988081 is 1808891281.

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.

It is a cyclic number.

It is not a de Polignac number, because 1821988081 - 2¹³ = 1821979889 is a prime.

It is a super-2 number, since 2×1821988081² = 6639281134612125122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1821983081) 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, 4577661 + ... + 4578058.

It is an arithmetic number, because the mean of its divisors is an integer number (457786000).

Almost surely, 2^1821988081 is an apocalyptic number.

It is an amenable number.

1821988081 is a deficient number, since it is larger than the sum of its proper divisors (9155919).

1821988081 is an equidigital number, since it uses as much as digits as its factorization.

1821988081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9155918.

The product of its (nonzero) digits is 73728, while the sum is 46.

The square root of 1821988081 is about 42684.7523244542. The cubic root of 1821988081 is about 1221.3735495191.

The spelling of 1821988081 in words is "one billion, eight hundred twenty-one million, nine hundred eighty-eight thousand, eighty-one".