81984890 has 32 divisors (see below), whose sum is σ = 160359696. Its totient is φ = 29998080.

The previous prime is 81984853. The next prime is 81984911. The reversal of 81984890 is 9848918.

It can be written as a sum of positive squares in 8 ways, for example, as 786769 + 81198121 = 887^2 + 9011^2 .

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11900 + ... + 17480.

Almost surely, 2^81984890 is an apocalyptic number.

81984890 is a deficient number, since it is larger than the sum of its proper divisors (78374806).

81984890 is a wasteful number, since it uses less digits than its factorization.

81984890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5714.

The product of its (nonzero) digits is 165888, while the sum is 47.

The square root of 81984890 is about 9054.5507895202. The cubic root of 81984890 is about 434.4214619314.

The spelling of 81984890 in words is "eighty-one million, nine hundred eighty-four thousand, eight hundred ninety".