1981209911 has 8 divisors (see below), whose sum is σ = 2047822800. Its totient is φ = 1915698240.

The previous prime is 1981209863. The next prime is 1981209943. The reversal of 1981209911 is 1199021891.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981209911 is a prime.

It is a super-2 number, since 2×1981209911² = 7850385422889255842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981209961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 271646 + ... + 278843.

It is an arithmetic number, because the mean of its divisors is an integer number (255977850).

Almost surely, 2^1981209911 is an apocalyptic number.

1981209911 is a deficient number, since it is larger than the sum of its proper divisors (66612889).

1981209911 is an equidigital number, since it uses as much as digits as its factorization.

1981209911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 550609.

The product of its (nonzero) digits is 11664, while the sum is 41.

The square root of 1981209911 is about 44510.7842101215. The cubic root of 1981209911 is about 1255.9629569636.

The spelling of 1981209911 in words is "one billion, nine hundred eighty-one million, two hundred nine thousand, nine hundred eleven".