81919420 has 36 divisors (see below), whose sum is σ = 189097272. Its totient is φ = 29788000.

The previous prime is 81919373. The next prime is 81919421. The reversal of 81919420 is 2491918.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81919421) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 14506 + ... + 19345.

It is an arithmetic number, because the mean of its divisors is an integer number (5252702).

Almost surely, 2^81919420 is an apocalyptic number.

It is an amenable number.

81919420 is an abundant number, since it is smaller than the sum of its proper divisors (107177852).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81919420 is a wasteful number, since it uses less digits than its factorization.

81919420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33882 (or 33869 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 81919420 is about 9050.9347583551. The cubic root of 81919420 is about 434.3057936774.

The spelling of 81919420 in words is "eighty-one million, nine hundred nineteen thousand, four hundred twenty".